Finger in butthole for the first time

Ne
Hey guys! My boyfriend and I have been thinking about having anal soon... So today, he tried putting a finger in. Very slowly. Very gently. He was great. And it felt GOOD! I didn't expect it to feel good! At the beginning, it was like a massage, relaxing and making me want to sleep. But after that... Gosh... It felt so good... 
But I was thinking the whole time " what if he gets poop on his finger? " and " what if his finger smells when he takes it out? " and such things! So I'm a little afraid to tell him it felt awesome... Maybe he didn't like it 😶 Hm... 
Oh and! Now my butthole feels strange! Like I want to poop! But I don't! Is this normal? ( we did the finger thing four hours ago )
And one more question. Could my butthole become weird? Could it get larger and STAY that way? Hm. I'm a little bit afraid of having anal. I mean, a finger is okay, it didn't hurt ( or only at a moment but it wasn't a horrible pain, I barely felt it ), but... My boyfriend is pretty big if you know what I mean and... how it it supposed to go in?! 
Thanks in advance!