Anal...

So my bf of almost 3 years is really kinda down for anal. We did it once, like 1 year into dating, but I absolutely hated it! Even though we used a lot of lube, it was very painful, almost to the point where I was going to cry & just thinking in my head "when is this going to end?".
4 days ago we were taking a shower & everything was super hot & steamy. We were really into just us in the shower together but than all of a sudden he asks me if I'm down for anal today. Part of me wanted to say yes for the simple fact of watching & hearing him get so much pleasure out of it, but I couldn't do it. We did do it & it turned out amazing for the both of us (he couldn't stop talking about it all weekend). I just don't want to be afraid to do anal...any advice?