Hi bumbly, I've followed several of your threads simply because I remember finding the first few weeks with my DS equally hard. Sorry to hear that you are still finding it so difficult.
Firstly, have you got a decent HV you can talk to? Mine was good - my PND score was really low at six weeks but by 8 weeks was sky high. My GP was great at offering support and my HV came weekly for a few weeks just to listen and tell me I was doing okay.
Secondly - being a new Mum is really hard. I know you are probably hearing this all the time but it DOES get easier. I think the first few weeks with my DS were the worst. I can rememember trying to fill in a "routine" for the nursery I was applying for (even though he wasn't due to start there for another three months) and thinking "routine - he doesn't have a fecking routine". Of course by the time he started there was a sort of routine.
Thirdly, if your little one is crying constantly have you ruled out reflux or transient lactose intolerance as your DS sounds uncomfortable. If it's reflux then Gaviscon is good (your GP can prescribe). If it's transient lactose intolerence then Colief is excellent - even if it is £10 a bottle (you'll find it in Boots).
Whatever else happens make sure you really have some time to yourself each day. Get your DH to take the baby while you go and soak in the bath for example.
I promise you that this will not last forever and you will get your life back and your nights of full sleep (at least until he's 3-4 and starts answering back).
Have you done a PND score with anyone to see if you are depressed. It honestly sounds like you need to do one. It might only be high because you are exhausted but at least you'll be offered some support.
Don't panic too much about raising your voice - we've all done things we regret doing and you sound tired out to me.
Oter advice here is excellent. When it gets too much put your DS safely in a cot then leave the room and calm down for 10 mins. I know he'll scream but he will be safe and more importantly you 'll get a chance to take a few deep breaths. This is hard advice to follow as if you are anything like me you'll feel guilty about leaving him but your sanity is important as is his safety.
Hang on in there. The Cry-sis line is a good one and I'll just go and find the number to post here. Keep coming back for support - we've all been in this position as the early weeks are really hard for most people.