Anal help

So I've never done anal before and I've been with my husband for 7 yrs when he gets his dick anyone around my ass I start getting scared lol he'll put the tip in and I literally feel like I have to poop so I tell him to get it out :( so we ended up trying again but someone told me for him to start with fingering your butthole? I'm like idk bout all that but he did it and after a while I didn't feel anything he was also playing with my clit at the same time it started getting better that when he took his finger out my butthole he said there was a little smear of poop okay that's just fucking embarrassing. Any advice guys? He wants to do anal so bad but his dick to thick lol