I want to wait, but I am afraid that if I make the guy wait, would if I am bad in bed? What if there is some other problem? I would feel bad making him wait, marry me, and then the sex is bad.
1. If he truly loves you, he will wait with you until marriage, and he will never pressure you before marriage. If he is pressuring you into sex before marriage, little to no good will come out of continuing a relationship with him, because he is only pursuing his selfish lusts and not protecting your heart.
2. People set a false ideal that on the wedding night that sex is the most amazing and intense thing there is between husband and wife. This is borderline idolatry. Sexual intercourse is not the pinnacle of marriage, and if you set it to be, and then find out that it is not, you will be devastated. If God is not the core and life of your marriage, you will eventually fail.
Sexual intercourse within marriage is a journey, as all of the marriage is to be. Sometimes it is amazingly awesome, other times it is a struggle. You could indeed have problems, and many married couples do, because bodies change and emotions change. But the point is that the 2 of you have made a covenant bond together to walk through it together.
Far too many people believe that once 2 people get married all of their problems and sins go away. This is simply not true. Whenever 2 sinners saved by grace come together, you will walk together and grow and change through the sanctifying process of grace. Marriage takes work and effort, but it is one of the greatest works you will ever do in life in the process of sanctification.
No one that I have ever known that waited until marriage has ever honestly said that they regretted waiting for marriage.