What do I do?

[CieloAzor]

Preflop, limping behind with 54o is not as terrible as has been said, but it's usually uncalled for, and not a good habit for a beginner to get into.

Personally, I like the flop bet. The BB's check-raise probably indicates that he flopped 2 pair a lot of the time, but even if it's just a 6 or 7 that didn't believe you, you're still drawing to straight outs only. Given the meager odds/implied odds you're being laid, I really don't think you can call. He's usually gonna stick the rest of his stack in on the turn so you're only paying for one card.

If he had raised to 200 or 300, I call for sure and try to stack him. I think check/folding the flop is pretty silly.

Turn is an easy fold.