Seeking Advice on Adult Activities (NSFW)

Ok, so, I'm looking for some advice about, well, anal. If this is the wrong place to post this I will happily move it. With that outta the way, I'm looking for advice on how to make it not sting. I had a boyfriend a while back for about two years and it was never a problem. But now, years later, I can't really pull it off and that is frustrating for both me and my wife. Oh yeah, I have a wife now. I also want to be able to, well, use toys, but again, it always stings. Is it not enough lube? I'm not relaxing enough? Could it be as simple as I'm out of practice? Please help.