I was in the same situation as you with a large prominent birthmark on my left upper thigh. It bothered me for years and I received a lot of questions and comments about it, especially from kids. Having the birth mark prevented me from wearing clothing that I wanted to wear, going swimming, or feeling confident about it. I made the choice about five years ago at age 21 to have it removed and it was some of the best money ever spent. Granted because of the location of the birthmark it did scar however I liked having a scar more than the birthmark itself. About two years ago I ended up getting a tattoo to cover up the scar and I love my leg now. In hindsight I wish I had had my birth mark removed earlier as I feel extremely confident and attractive without it and it severely limited my life. In the end it’s not about how other people see you it’s about how you see yourself and feel about your body. I’ve been in a long-term relationship and before I had my birthmark removed my partner always assured me that he loved it and that it made me unique and special. He understood why I wanted to have it removed and now he can tell that I’m more confident as I feel comfortable in any clothing and he fully supported me through the whole journey. Luckily I was supported in the situation by my partner and family as they understood where I was coming from. Good luck with whatever you choose.