If he is new and may have health concerns I would get him to a vet for an initial check-up. So much of watching your rabbit's health is looking at what has changed from the normal, and with a new bunny you don't know what is normal yet. I also like new bunnies to be seen by a vet so you can get a first opinion on any problems they might be coming to you with, and to make sure they're not carrying parasites--external or internal. GI parasites could definitely make his poop different. An annual exam is essential for bunnies and I like to start that with new ones as soon as I get them.
Since you don't know about his habits, the small poos could be somewhat normal, but they might not be. The stress of moving to a new environment can cause stasis too.
Add some pedialyte to his diet for sure, a nice bowl full of it in a fruity flavor or unflavored with a drop of grenadine works well, and some probiotic, if you don't have the funds for a vet right now. That should improve the poops, but if it doesn't this becomes a vet-only situation.