I'm not allowed to diagnose people on here, but if you NEVER talked in groups--not saying a word--then that in itself is not necessarily indicative autism. The big question is WHY you didn't talk to other people. Did you just not know what to say?
Hearing impairments aren't indicative of autism, either. I've heard of people who were misdiagnosed with autism when in actuality they had a hearing impairment--not quite deafness, but not enough to be able to hear much. There is a possibility you have that, but then I don't know if tinnitus contributes to that since I don't have that.
When you say that you got a stone in your head, do you mean that someone hit you in the head with a rock? That was probably what gave you tinnitus, since it happens with brain injuries like that. Furthermore, such an incident would not have been able to "give" you autism. It's something you're either born with or don't, although it's known as a spectrum disorder so it ranges in severity (I myself only have mild Asperger's, which is like a subtype so that's why it's in the same forum section).
Chances are you might not be speaking much because you're not able to hear people or judge the volume of your own voice. Unfortunately, tinnitus doesn't have a cure, so there's no way to get your hearing up to normal levels to determine whether or not you have autism.
But here are some questions you can answer that can determine it. I'd also consider going to another doctor for a second opinion, and explain your medical history with the injury and your hearing problems.
1. Do you have trouble making eye contact? Do you forget or is it just painful?
2. Are you easily "overwhelmed" with intense smells, tastes, or textures? As in, are there certain things that you just CAN'T touch or smell because you just can't stand it?
3. Do you ever feel alone even in a crowd of people?
4. Do you feel like no one "gets" you, and you can't make friends with anyone?
5. Do you look at all the people around you and wonder why they all seem to act a certain way?
6. Do you have to ask people what their mood is because you can't tell--in your case, your family?
7. Have people ever told you that you are often insensitive, rude, or bluntly honest?
8. Do you sometimes feel like you have to do this certain physical movement over and over again when you're forced to sit still, like flapping your hands, feeling some part of your body with your fingers, twiddling your thumbs, etc.? (Not all the time, just when you're bored and aren't doing anything with your hands?)
9. Do you have difficulty lying to someone?
10. Do you have to have a schedule planned out for the day and feel distressed when you aren't given specific instructions as to what you should do?
11. Do you feel like you have trouble remembering that other people don't necessarily know what you do in situations?
12. Do you feel like an alien who just doesn't quite fit in with human society?
13. Do you love rules and hate it when people seem to not follow them or contradict themselves?
14. Have people ever told you that you have an eye for detail?
15. Do you have a tendency to misunderstand people when they're making a joke and take their words a bit too literally? Like if someone said something offensive or creepy (but clearly meant it as a joke), would you not like them for making that joke?
16. Do you have poor coordination and balance and have to "watch where you're going?" Have you been called "clumsy"? Because your inner ear controls your balance, you might have poor balance because of your injuries. But if you were clumsy before getting hit in the head, then it could be autism--although not everyone who has poor coordination is autistic.
There are other symptoms, but chances are you could be exhibiting them because of your tinnitus and you can't hear well. Or it could be because you really are autistic. Or both. I'm leaning more for hearing-impaired, though, since if you were hearing-impaired you wouldn't be able to understand the ebb and flow of conversation, not because you wouldn't be able to read social cues like an autistic person wouldn't but because you would have trouble hearing when it was your turn to talk. And you wouldn't talk much if you weren't able to hear people talking very well. And if you had trouble understanding people then you'd naturally be introverted and not want to talk to them because you'd have trouble understanding them. Social anxiety is usually seen in higher-functioning autistic people, but you don't have to be autistic to be socially anxious or shy. And you might not be able to communicate with people well because you couldn't hear them. If that's the reason, like you can't hear their words well, then that's just tinnitus. If you can't understand their facial expressions, forget to sort of look for them, or you can't quite interpret their tones of voice, then that's more likely to be autism.
Your second doctor is going to need to factor in your tinnitus. There could be a chance that you are merely hearing impaired. Do some research on autism and see if you can identify with people that have it. If you don't quite get how "we" think and don't feel like you think that way, then you're not one of "us". Autism spectrum disorders affect how you think, and that's why we process information in a way that isn't quite compatible with regular people. A lot of tests that could determine if you have autism assume that you can hear normally (I myself often find myself saying "what?" but everyone in my family does that, lol
). So be sure to try and get your doctor to only make you take some sort of test that would make your poor hearing abilities irrelevant.
What do you intend to accomplish with this, exactly? 
