First off: Your boyfriend cheated on you because he is selfish, inconsiderate, immature and can not control himself, not because you are wet. Better to get a boyfriend that loves you and does not hang around you just for sex and his own gratification.
There is not much you can do about it. Some women are just made that way. I have some friends that have to use pantyliners all day every day to keep dry. It is just a part of their lives now.
There are some prescription medicine that can be used off-label to try to dry it up a bit. Speak to your doctor. Using prescription medicine for long periods of time is however not healthy if the problem is not major. If I were you I would anyways go to see a doctor to have my hormone levels checked up and look for possible infections.
You can also do some kegel exercises to strengthen the vaginal entrance muscles to give more friction. These exercises will make sex better for both you and your partner, immaterial of how wet you are.
One of my 'wet friends' also switched to anal sex once in a while. Do not feel pressured to do this. Many women will have nothing to do with it and that is OK. It is however an option to consider. Be very careful with it and do your research before you attempt it. This is not an endorsement of anal sex. It is a personal decision for you to make.