Sleep advice needed!!

Ashleigh • TTC #2!
Hi! My handsome little boy is just over 4 weeks! He always seems a little restless when he sleeps and never goes over 2.5 hours! Day or night! He still is only taking 2 ounces (he spits up if he eats any more). 
It seems like most people's 4 week olds are sleeping for slightly longer periods. 
Anyone with a similar experience/advice?! 
Thanks so much : )