I didn't say sexuality was a choice. Humankind (and all creation) are created heterosexual. Some humans, due to various reasons get a gay mindset. This may be because of child abuse, being taught about homosexuality at such an early age as to confuse the child, or even reading / watching homosexual material at a young age that confuses the person and makes one think that what they are feeling are gay attraction when actually it is not.
For example, according to child psychology, children first have admiring feelings for persons of their own sex before they start having sexual attraction to the opposite sex. These feelings of admiration (for someone of their own sex) are simply that - feelings of admiration. The child may look up to this person and want to be like them. BUT when a child has previously learned about homosexual feelings (for example, in kindergarten as is now customary) IT'S POSSIBLE FOR THE CHILD TO CONFUSE THE FEELINGS OF ADMIRATION WITH FEELINGS OF BEING IN LOVE!!!
Children are inexperienced and don't know what love is. It would be very easy for them to confuse the feelings. And being upset by this and unable to understand their feelings, they would be preoccupied with the thought, defining every feeling to be a sexual attraction. And it's possible that some, thinking that one can get attracted to their own sex, accept these feelings and act on them. They may start reading homosexual material and watching homosexual movies. These don't have to be X-rated. Such shows/books may be made for the general audience including children but would further cause the child's mind to be misled and cause them to further develop homosexual feelings.
So the first thing for you to do is to accept that homosexuality is not normal human tendency and you can't be a Muslim if you engage in homosexual behavior OR HOMOSEXUAL THOUGHTS. So long as you haven't accepted this, you can't change and can't expect God to help you change. This is because you accept homosexual to be a correct way of life.
But either Islam is correct or such thinking is correct as both can't be side by side. If you believe that your belief about homosexuality is correct, then you expect islam to be incorrect because islam does NOT allow homosexuality and states that homosexuality is a deviation.
Thus, you first need to correct your belief.
Then you need to decide that you can NOT live with such a life or such a mindset and must absolutely try to get a heterosexual mindset. You must make every effort to do so no matter what. Here Shaytan shouldn't succeed in reminding you your previous homosexual actions and stop you from proceeding. Expect that the Shaytan will remind you that you engaged in such and such action (as he always does) and therefore you can't improve your future because of your bad past. Do not allow this to hinder you. Tell yourself that you will be judged for those thoughts and actions from this day forward. As for the past, seek forgiveness for it and expect that Allah will wipe your slate clean.
Do not engage in any homosexual activity or thoughts. Do not read or watch any homosexual material. Do not meet anyone that reminds you of your homosexual acts or causes you to get homosexual urges. Do astaghfirullah a lot and do not let any thoughts related to your sexuality enter your mind at all. Stay far away from your past partners. If possible go to a different city or country, preferably where homosexuality is not allowed.
Get married. YES, GET MARRIED to a woman. You may or may not have to disclose your past depending on your situation and the woman. Some women may be accepting and will accept you. When you're married, live with your wife and don't allow your mindset to cause disturbances to your marriage. Love your wife as best as you can and continue to seek Allah's Help. Do not hate your wife and do not consider her an obstacle to your happiness. Try to appreciate the beauty of the married life, your wife, etc. Also, practice Islamic obligations fully, such as the 5-times daily prayer and fasting, etc. With time, and with Allah's Help, your natural heterosexual feelings will take over, wiping out homosexual tendencies.
Oh yes, and you must absolutely detest (hate) homosexuality as a grotesque and unnatural and filthy action.