Anal Sex . questions

So my boyfriend really likes anal and me and him have only did it once before I got pregnant currently am 9 months pregnant and I really want to please him by doing anal when we did it the first time it was alright a little painful and uncomfortable but now when ever he goes to even put a finger it it hurts / I just feel like I have to take a big poop is it normal to feel that way ? Sorry I'm just so scared that I'm gonna like poop on him or something. Girls please give me some pointers.