My first answer is to talk to your pediatrician. My son actually had the same issue up until he was about a year old, then one day it just stopped. I didn't get much help from the pediatrician other than checking his stomach for a blockage and telling me that he is just going to outgrow it. It was so hard to travel with him or go anywhere for any length of time because he would get hungry and feeding him in public was hard with him spitting up so much. Since there was nothing medically wrong with him, I tried a variety of things. The only thing that worked for my son was adding yogurt to his milk, gerber used to have a yogurt cereal (I don't think they sell it anymore though). There might be a replacement... But that seemed to help reduce the amount he was spitting up (at that point little spitups are better than what we were cleaning up), it also seemed to make him feel more comfortable and less irritable.
Many people told me you should never put cereal in a babies milk, but it was the only thing that worked for us and I would only put in about 1 - 2 tsps for about 4 - 6 oz of milk. I tried switching formulas, even switching to soy milk. No luck...
For the constipation...prune juice worked(in small amts unless you want an explosion). Gerber sells small bottles, i would just give him a few sips to see if it works.
Again, its just an opinion, it worked for my son..I know it goes against what is out there but when I told my pediatrician what helped my son he didn't see a problem with it since his weight was normal. Just make sure you follow what your pediatrician says.
Good luck, hopefully you find a solution!