ah!! dont know what to do!!

so i posted a thingy a couple months ago about me and my bestfriend.. i havntdone anything but about 3 weeks ago he started sending me dick pics saying "i just want ur opinion on it and he wanted to know if its normal or small" and made it very clear that he just wanted it kept between us. i promised and continue to no tell anyone ( first time discussing it is this post) but when i askee jokingly if he wanted one of mine he said sure.. a couple night ago he sent me a video of him masterbating..as well as a picture..i then askes if he wantes a video of me masterbatingand he said sure... the problem is that he has a girlfriend... ive been in love with him tho for over 2years... and idk what to do... should i tell him i like him and risk our friendship or just let it run its course... btw for more information check not my last post but the ine before that