Hi and thanks for your letter.
I've received a lot of letters from young people who are going through a similar experience to you. No one should be targeted or bullied for any reason.
I was just wondering if you were feeling uncertain about your sexuality? You mentioned that you are unsure if you are gay, then said that you know you are gay. It sounds as though your feelings are trapped inside and not yet clear, which must be really difficult.
It's good to read that you have someone who you feel is supportive and who listens to you. Perhaps at this time you might want to get some additional support to speak more about this? If your parents are not aware, have you thought about speaking to them? They might be able to provide you with a lot of support and understanding.
If talking to your parents is not an option have a look at BGIOK (Being gay is okay) or Young Person's Advisory Service, both of these websites offer information and advice to young people about sexuality. You may also want to have a look at the ChildLine message board on sexuality - you can post a message and see what responses you get from others.
Hope this helps
Sam