Sex and pregnant

It’s a bit of a TMI. I am 18 weeks pregnant and pretty big so we are limited on sex positions. The last time my husband and I tried to have sex he was in but I couldn’t feel him, he is very well endowed and I am usually to tight or petite for him but this time he said I feel huge like he couldn’t feel the side walls or anything and I couldn’t feel him at all. Has anyone else had vaginal stretching like this? I feel so weird like I didn’t think he was in me at all! We tried a couple different positions but nothing made a difference! Anyone else know about this?!