Omfg I almost came

So. I really need to share this with u girls!
My boyfriend and I had sex on Friday and it felt so good! Which is weird because that was the fourth time we had sex, and the first three times were naaaaah not so good, not good at all ( except the emotional part, you can understand me ) but on Friday it was BOMB like really, I swear I almost came! But then we had sex on Saturday morning, evening, Sunday morning and evening and it wasn't so good anymore. Any explanation?
And why did it feel so good on Friday while he didn't change anything? I don't get it!