This guy really likes me, but i really like my bf?

Theres this guy taylor, he really likes me... he keeps telling other ppl how much he likes me and how sad he is that me and my bf got back together... last yr during swimming, he touched my as$ in the pool (we were swimmin for gym class), he always stares at me, has asked me out (i always say no), asks other ppl for my cell #, keeps trying to chat wit me, stares at me, etc. hes making me really uncomfortable. i have talked to him, and my bf has told him that he needs to back off, but he just wont. it makes me feel awkward and uncomfortable. i feel bad that hes so hung up on me, but i have already told him to back off that im not interested, so im not leading him on. I feel like ive tried everything... any ideas....??? HELPPPP please <3