Can constipation cause upper gastric pain (pressure/stabbing) mainly on the right side? Also gas & bloating after eating. Passing gas with eating fennel. Gallbladder already removed. I also have gerd.

Yes. Yes it can. Check and review these issues and possible dietary and other management issues with your doctor.
Yes. Constipation can cause that pain and pressure, bloating and passing gas that you describe. Try eating a lot of fruits and veggies for roughage and drinking 64 ounces of water. If that does not work natural calm works probably the best that I have found. It has magnesium in it and you can start with a teasoon and work up to the amount that works for you and it will keep you regular and feeling good.