This is a tough matter, and unless someone knows the language you're speaking (if it is an earthly language) no one can say for sure if it's true tongues or false. I believe there is such a thing as an imitation tongue, but i don't want to worry or concern you. Just pray about it and use your discernment, no one not me not anyone here not a pastor can tell you if what you're praying is genuine tongues, that is between you and God, but if it is something negative you'll know.
I speak from experience. I spent years wanting to speak in tongues and i had many people lay hands on me. Then later i started feeling bad and dizzy after praying in tongues. I believe i got a false tongue sadly and have since not prayed in tongues. I 100% believe tongues are real i'm not doubting, rather i know that the enemy will try to imitate. I had to use my own discernment to stop, and it wasn't easy to decide because to this day i longed to speak in true tongues, but i felt HORRIBLE when i prayed in what i believe now was a false tongue.
The best way to know that you have received the authentic ability to pray in tongues is to follow the Scriptural steps to ask and receive anything according to God's will. If we follow the steps below, there is no way that you will receive anything different than the real thing. This is promised by what Jesus said, "If an evil man knows how to give good gifts to his children, how much more does God know to give the Holy Spirit to those who ask Him?" Previously He said, "If a child asks for bread, will he be given a stone? Or asks for fish, will he be given a snake?" Of course the logical answer is "no". So here are the steps.
1. You need to know that the ability to pray in tongues is God's will for you. Paul, speaking by inspiration from the Holy Spirit said, "I would you all speak with tongues". That pretty well settles it from Scripture.
2. Then you need to ask for the ability to pray in tongues. Phil 4:4-6 says, "Everything by prayer and supplication with thanksgiving, make your requests known to God", and, "If you ask for anything according to the will of God, you will receive it."
3. Next you need to say to the Lord, "I receive the ability to pray in tongues". This is supported by, "He who asks receives." As soon as you ask, God hands it out to you. By faith you take it from HIs hands.
4. Believe that you have the ability to pray in tongues. You prove that by activating your faith by making up a language you have never learned. Some object, saying that it is not of the Holy Spirit to make up the language. I say, "How can you activate your faith unless you try to make up a language?" What happens when you try, although it may be a bit hesitant at first, the rivers of living water starts to flow out of you in an expressive, articulate, fluent language where you lose the sense of trying to make it up because the words are now flowing out of you in a language you know you are not making up.
One way of helping the flow to happen is to think of a serious prayer request where you need to intercede for someone in real need. Ask the Lord to guide you tongue and while thinking of that person start to pray for them in the language you have not learned. When you start to intercede in the Spirit, the language will come and it may surprise you the depth and fluency of the language that comes out of you for that person. After a while you will get a witness in your spirit that God has answered that prayer and you will get that peace of God that passes all understanding that the prayer has been heard.
The accompanying emotions that I have witnessed when someone has started praying in tongues is a sense of joy and peace and a new sense of the reality of God. But we don't depend on those emotions and senses. We depend on our faith in 1 Corinthians 14:2 where it says, "Those who speak in tongues speak to God, hence no man understands him, but he speaks mysteries in the Spirit."
There is always a definite purpose in praying with tongues. We don't pray just for the sake of it. Either we pray because we have a desire just to fellowship with the Lord in the Spirit. Paul says, "I pray with the understanding [my own language] and with the Spirit [in tongues}, I sing with the understanding and sing with the Spirit." Or we want words to express our praise and devotion to the Lord and find that we don't have words to give Him the praise He deserves, so we ask him to give us the words to praise him and then give our praise in tongues. As I said before, when we see the need to intercede for someone, we need the tongues language in the Spirit to break through the hindrances and get the victory for that person. Tongues is a powerful tool for that. Once, I was told about a woman in hospital with serious bleeding in her stomach and the doctors couldn't stop it. They were in fear for her life. This was around 2008 just after I joined CF. It was a member's mother and he asked me to pray for her. So I asked the Lord for the most powerful language to intercede for her. The language I got was a very fast Oriental type language. After 20 minutes I felt really drained and hollowed out with the intensity of the language, No way I could ever have made up a language like that. Then I received peace and the language stopped. Later, I found out that the woman in the hospital in the UK, and I was 12,000 miles away in New Zealand, that the flow of blood stopped at the exactly the same time as when I prayed. It was 11am in NZ and 11pm in London. I saw that as a miracle of intercession, and it was achieved through praying in the Holy Spirit.
So, if you follow the Scriptural steps of asking and receiving, there is no way you can get false tongues. God will give you exactly what you ask for. I can see how you got false tongues in the first place, possibly because you followed someone else's advice and didn't go through the Scriptural steps. But I can assure you that if you follow those Scripture steps that I have outlined, you should have no fear of receiving anything but the real thing. And you won't get any strange manifestations with it, because praying in tongues is an act of faith in God's word in the asking, receiving and using the ability in the way God designed it.