What if I feel like my friend only hangs out with me to be nice?
That would be bad. What has he done to make you feel that way?
He has a lot of other friends he hangs out with more from the office
Do you think maybe he hangs out with other people more because you're constantly questioning your friendship?  Be a little more trusting and you might find you two spend more time together!
That could be true.
It might. People do not like it if you don't take them at their word and you keep questioning them. You should trust what they say.