My f buddy keeps flaking...?

well hes not an "f" buddy... well he kinda is..lol idk. well he was one of my bestfriends before anything ever happened.. last year i broke up with my ex of 4 years and i was having a really hard time with it, and my friend was always there to comfort me and somehow we started having randomly. like after we'd hangout with all our friends we'd usually end up sleeping together at the end of the night.. well i got a bf and we didnt do anything because im not a cheater, and as soon as i broke up with him... (this was the deal with my buddy) i let him know and sent him a pic. we had within 3 days and then he asked me to have a ... that went ok except by the time itr was my turn he was limp... well we've tlked about meeting up 3 times since then and every single time, hes flaked.. and every time they've been his idea. like hey whatr u doing tonight? then ill say well i can come over, then he wont txt back when it comes down to it, or he will say hes tired. or like tonight, he said to come over then 5 min later he said wait hold that thought meeting up with an old friend.. then i was like ok another time :) he said "maybe" and thats it. hes confusing... i could care less if we never slept together again, at this point, i miss my friend.... but its almost lke i need to sleep with him to be close friends... idk? any advice? hes 25 and im 18... so no one knows about this. "affair" or whatever it is.