I'm someone that has had SERIOUS issues with anal play. Here's what helped me.

First of all, STOP trying to force it. When you are not relaxed, your muscles tighten and it will hurt even worse. I cannot repeat this enough: DO NOT FORCE IT. Not only will it hurt worse, you run the risk of tearing something or really hurting yourself. It should NOT be painful.

As for the pooping feeling, it was something that I used to have, too, when first experimenting with anal play. When the only time you've ever had your sphincter opened is when you're having a bowel movement, you associate the feeling of your sphincter being opened with a bowel movement. Totally understandable. As long as you go to the bathroom beforehand, or if you're really paranoid about poop, give yourself an enema, you will NOT explode all over your boyfriend. But do try to make sure you've gone to the bathroom beforehand.

Do NOT use any numbing creams or agents. Pain is your body telling you that something is wrong and if you cannot feel anything, you also won't be able to know if something rips or tears. If it hurts, you are doing it incorrectly.

Lube, lube, lube. Use something with about the consistency of hair gel. Many people like Maximus for anal play.

Warm up first. Warm up with fingers, starting with one and then adding more. Let your ass adjust to having something in it. It's initial response may be to tighten or reject what's being inserted, but breathe, relax, and give it a second to adjust. It will. You may feel momentary discomfort, but breathe through it and your ass should adjust. If it doesn't, take it out. I'd also recommend purchasing a butt plug. Use it on your own, at your own pace, and get used to the feeling of having something in your butt. My first "real" plug was the Tantus Tulip plug, and it was perfect for me.

Relax. If you are nervous or scared or anticipating pain, your sphincter will reflexively tighten, making it not only either difficult or impossible for you to insert anything, but also horribly painful for you to do so. You really do have to relax because otherwise you are just fighting your body.

Finally, you have to want to do it. Don't do it because your boyfriend wants it. Do it because you want it. If it's not something you really want, your body will not respond in a positive way. Playing on my own with my fingers and a plug was really beneficial for me. It let me learn my own body and what I liked and could handle at my own pace, and I didn't have to worry about disappointing someone else. Play on your own and see what you like and what works best for you. less