Burping

Is burping a baby something that every parent has to learn how to do? I thought I had it down pretty well, but I can only get Katy to burp about half the time. Is it bad for her when I can't get her to burp? I know it causes more spit-up, but I just can't seem to get those bubbles out of her system. Sometimes she'll burp so nicely for me, I hardly have to even tap her back. And sometimes it seems to take me forever, meanwhile, she's falling asleep on my shoulder and I have to wake her back up to keep feeding her. Please tell me this is normal. It's starting to drive me crazy and I'm slightly worried that I'm not burping her properly. I love her and wouldn't trade what I have for anything, but sometimes, being a mom can be absolutely exhausting!