You’re likely experiencing these symptoms because you’ve never properly dealt with the abuse. You’ve blocked these memories from your life for a very long time. Unfortunately, your flashbacks have increased and intensified. You can only block these memories for so long and then, as you are currently experiencing, they’ll become more intense and frequent, to the point where you have no choice but to address them. I think you’re at that point. No longer can you ignore these memories.
The best way to handle this situation is to consider therapy. If you do choose to attend therapy find a therapist who specializes in helping individuals who have experienced sexual abuse or trauma.
In the meantime, remind yourself that these are flashbacks and not your current reality. Tell yourself that you’ve survived the worst of his abuse and it is now over. No longer do you have to be a victim to your uncle. When the flashbacks occur you can also try a technique called grounding. Grounding means that you do something physical to bring yourself out of the flashbacks such as stomping your feet or waving your arms. It would also be helpful if you considered finding some form of support either through friends or family or joining a survivor’s support group.
As for whether or not getting involved with “drugs and sex” led to you to being molested, the answer is no. Based on your letter you were molested when you were three years old. I don’t see how your involvement with drugs or sex is related to you being molested as a very young child. Perhaps you left some details of the abuse out of your letter and I’m not making the connection. The bottom line is that you were molested by your uncle. None of it was your fault nor did you bring it on yourself. What he did to you was abuse and it was wrong. He took advantage of you. What he did was also illegal. He could go to jail for abusing you. Your parents should be aware of what he did to you and so should the police. I hope this helps.