Pressure

It may be because you are putting a lot of air up there, which can cause a bloated feeling. If you're talking about the sensations post intercourse that does take a few days to subside. I used to enjoy that as it reminded me of the fun I had and how good the sex made me feel. The reason that you're feeling like you have to use the toilet is that your rectum was stimulated with something firm, which normally is stool, so there are messages going to your brain telling you that you need to use the bathroom. Nothing to worry about.