Most Helpful Girl
You don't have to wear anything under it although if you end up wanting to take your sweater off you'd be a bit stuck.
I hate wearing multiple shirts as well, I try to keep it simple, I just can't stand feeling stiff or stifled under a bunch of shirts.
If I were you I'd just wear a cami underneath, and tuck it in. But if you don't feel like doing that then just wear the sweater by itself, that should be fine.