Wow, M.! You've got a lot going on and must be so-o-o frustrated!
It sounds like this may very well be situational but there's also a strong chance that your son could have some special needs, like asperger's syndrome or mild autism. I think you should investigate this if only to rule it out, especially after what your mom said. I'd see if your county Intermediate School District could evaluate him for you. They have a lot of early intervention programs that are government-funded then they'd continue to work with him as he grows. You could also have him privately evaluated but it sounds like you couldn't afford that. There are some early-on programs thru other community organizations, like the county community mental health and public health agencies. You can speak to his doctor too to get an opinion there. Head Start is trying to get a grant to work with 0-3 yr olds in the fall. You might check with them too.
I'm wondering if, as you seek an evaluation of him, you could take this summer to see if you can give him an extra- strong dose of touching and affirming, mainly with you, and lots of verbal calming and reassurances. Keep him with you even more and focus on him so he feels more bonded with you as his #1 caregiver. I actually think it's good that he sleeps with you. Sounds like he feels out of control quickly. This definitely is not a child who should be left to try to cry it out. Must be terrifying for him! He's got something important going on and it's going to be up to you to find out what it is and meet his needs.
I'm glad you have a lot of support. This would be worse probably if you were alone with him all the time. He definitely is a high-needs baby! Recognizing that is the first step to getting the help you need to love him through life.
God bless you, M.! You can do this!