Advice requested

Hi lovely people,

I just want to get something off my chest and hope I get some tips.
I’m a mom to a son who is now 4 months and 3 weeks old. He still has huge amounts of colic! Always had it.. whole days of crying from the pain. I’m often alone and dad is only there in the evenings but can’t help him as much as I do, so I massage him myself and do the cycling legs exercise etc. He never drank his bottles nicely and it turned out he had a bladder infection recently, hence the crying moments during feeding. He had an antibiotic course and he was really cheerful again! They had already warned me that he could get cramps from the antibiotics but this wasn’t the case with him! Due to the diarrhea several times a day he was even free of cramps!! I was sooo happy! but it didn’t last long and the cramps returned with full force. I had swapped Infacol for Sab Simplex and it seems to help him well! So we should probably introduce solid food! I waited a long time with giving solids because of all the cramps.. I was just afraid he’d get more cramps. Now I think his teeth are coming in and mister drinks almost nothing. I’ve really received a lot of “good advice”. Okay that’s putting it very mildly I got yelled at! My mother-in-law is constantly on about it. His bladder infection needs a follow-up check because it doesn’t mean he’s rid of it just because of the antibiotics. Or yeah he needs another catheter, just double check. But he has no pain when peeing and no fever. I recently went to the ER at 8 pm just purely because I was attacked from all sides that it’s not normal for my child to overstretch and for me.. (he always cries at grandma’s, no idea why but it just is. I think it might have to do with the fact that she used to hold him while he cried and leave him, letting him cry quietly for an hour. And I assumed he was sleeping. Because she would call me if he wasn’t sleeping. And this happened multiple times.) .
I really need to give him solid food because the milk gives him cramps and this will help, just mash a banana with orange juice and give it.. I’ve explained 101 times why I haven’t given veggie purees yet and want to wait with this, just so if he’s cramp-free and suddenly gets cramps I know what he got cramps from. No she doesn’t want to hear this and has no interest in what I say. He’s four months old and is done with the milk and doesn’t like it.. but this was already the case when he wasn’t drinking and was 10 days old.. I’m soooo unhappy about this. From his cramps and now from this. I recently asked her after she called me specifically about it if I should stop the milk. No was the answer so she already sensed that the whole thing was nonsense because he doesn’t get enough from the first practice bites and still needs that milk he doesn’t like and gets cramps from, she gets cramps from milk herself so that’s fine! Sigh. I notice I’m getting more and more irritable and I don’t want that. Since he was born everything has been a yes-no game.. really over the dumbest things like the temperature and his clothes.. sorry but I can’t stand watching how a woman feels in menopause then I might as well take everything off. I always had a good relationship with her but I find it sad that she’s changed so much, how do I best deal with this? I find it quite difficult