Does this sound like BS to you? :/?

My bestfriend saw pics of my Boyfriend on Facebook. She said he was hot and she always said that she was jelous, even though she has her own boyfriend. Well, one day when i was out of town. She and him hung out without me knowing. Possibly because they knew i wouldnt be happy about it? Not that i care much, as long as anything goes down its all good. But anyways, so that day she had texting me and we were just chatting like usual, i had said "so watcha don?" She said "nm im with someone" I said "kool". Not having a clue it would be my boyfriend. A couple minutes later she said "Hey i hafta tell you somthn." I said " ok wat?" She said " Well.... i dont know if i should tell you actually, cuz ull be hurt". All i said was "noo i wont be hurt, mad, sad, or anything.. so just tell me". Even though, thats what everyone says just to get them to tell them. Ofcourse she didnt tell me till like a day later, when i forgot about it. She had called me up on the phone and said she needed to tell me something, she took a while to spit it out. But she had said she hung out with my boyfriend and he had kissed her. Supposably she had backed away yelling at him. But i know her personality very well, and she may be the type to kiss back. So i dont know what to believe. At the time i didnt know what to say, so i hung up till i calmed down. Then i had texted my boyfriend yelling at him that he kissed my bestfriend. He admitted it. I dumped him also, and i havent talk to her in days. His excuse was that he was high, and when hes high, he said he isnt himself and he does stuff he regrets and doesnt even mean to do. His mother even told me that. He kept begging for me to take him back and he was even crying. But when im high, even BLAZED, i know what im doing, and i can control my actions... sorta.. but the point is, is that i dont do things i regret. So what im asking you is: Does he sound like hes lieing? Does My bestfriend sound like shes lieing? Whats your opinion on this? I would also like some advice please... thanx <3