The anus, unlike the vagina, does not "stretch" as willingly. There are plenty of things to take into consideration before you start worrying on this too much, and I can speak well on this subject for two reasons. One being I'm a Nurse and two being, I love anal sex and have done with almost every sexual partner I've had.

Now, the bleeding is probably the breaking of blood vessels in that area. That can be normal with anal sex but it doesn't have to be. Your boyfriend needs to learn how to be slow and gentle with things until you get the right flow going and you should speak up for yourself if you're uncomfortable or if it hurts. And, I personally woudn't suggest KY for anal, or vaginal sex for that matter. For anal, if you're not using a condom, try an oil based lube. And no, I'm not telling you to stop using condoms if you are indeed using them. But, there is a product called "Wet" that I use for anal sex, it's the best lube money can buy when it comes to anal.

If however, condoms are being used, try what Aquaman suggested, lots of foreplay and anal play prior to penetration. And, don't try anything anal related for at two weeks. Give your body time to recover and heal, believe it or not, anal sex can be traumatizing mentally and physically if not done properly.

__________________
I did it all for the Nookie!