Congratulations on your little boy!
Sounds almost exactly like how my daughter slept at that age! In fact she hardly napped even when ON me, and only did longer shifts at night, never more than two hours if we were lucky. She hardly ever even fed to sleep just like your son. It's bloody tough, especially when everyone else's kids seem to be having a feed and then happily napping for ages. Obviously go back to GP if you're worried about reflux, but as other posters have said, it could just be developmental. Colic medicines and baby gaviscon didn't do anything for us unfortunately.
GOOD NEWS: From 5 months old her sleep improved a lot, from around when she started to roll. Basically as soon as she became mobile she was a lot more settled, I think partly because of a mild wind issue and partly because she has always been very nosy and was happy to be able to move around. I didn't do anything, she just stopped contact napping in her own time.
BAD (?) NEWS: Compared to other kids she still hardly (sometimes never!) naps at 18 months, but she's very happy and healthy. Now goes nursery a few days and often is still awake playing when older kids are sleeping. I've accepted that it's just how she is.
Hang in there, and if you are feeling miserable and anxious don't be afraid to ask for help for yourself too. And don't let any of these live laugh love types make you feel bad for not finding it easy. It's not, but it does get easier.