My best guy friend tried to feel me?

He's staying at ours for 2 weeks because his parents are out of town and I'm his best friend so yeah. We were swimming together in the backyard (we've swam together before but only at school, with the regulation swimsuit & swim shorts) and I was wearing a bikini. We were just playing around and stuff, he tried to untie my bikini top and it did come off ( the string) but he didn't see anything and I thought it was just an accident so I just left it at that. Then, while we were playing he lifted me up and flipped me over so that my back was facing him and he started drawing patterns over me and he did it over my (drawing circles) and stuff. He also offered to rub sun screen on me but I said no thanks cuz I was bit creeped out. Am I overreacting?