So overwhelmed and don't know what to do!

I love my son, I really do. It took us 2 years to conceive him so I know what a miracle he really is. I had the easiest pregnancy and relatively easy birth. But now 12 weeks later, I just don't know what to do. All he does is cry and fuss all day. I'm not exaggerating either, it's ALL day! He takes maybe 3 cat naps during the day. I said I could handle it because at least he was sleeping ok at night. But now he's not even doing that, he's up every single hour. I'm at my wit's end and spend most of my days crying with him. My husband is great and super supportive but he's at a loss too, and he has to work during the day so he really can't help at night. I'd normally turn to my best friend for support but she's experiencing a miscarriage right now so I don't feel right complaining to her. When I do find someone who doesn't mind listening, their advice  is just "hang in there, it gets better"...but when!? He's been like this since birth and is actually getting worse. Doctor has given him a clean bill of health, we've tried all the colic 'cures', nothing works. Has anyone been through this? Does it actually get better or do people just say that? When does it get better? I've been blessed with not having to go back to work and can stay home with him but now I'm wishing I had a way to escape but I know so many moms would trade places with me to stay home with their babies. How on earth can I possibly have another baby when I can't even handle this one? Feeling so lost and overwhelmed.