What to do??

[herestoafreshstart]

OK, I don't want to give too much away here but I'm really struggling and in need of advice! This is a long post; sorry! I really appreciate you taking the time to read it.
A bit of background; my DS was born back in April 2017 and was 10 weeks early. It was a very stressful start and he needed brain surgery etc. We spent 8 weeks in hospital and have had a rocky road since coming home but he's doing well now. During my pregnancy I suffered terrible HG and was off sick for significant periods of time. My husband is self employed and his work is weather-dependant so his income is unreliable despite his hardworking nature. (He's a great partner; very supportive and kind). We live in a small 2 bedroom flat in a fun area but it feels like it won't be long before we properly outgrow it.
I have 2 jobs; a teacher and an office based job. The money is exactly the same in both jobs (pro rata) and both are permanent. I returned to my office job in January (3 days a week) back in January and have found it fine. It's flexible and challenging but not stressful. I've just started back at my teaching job (2 days a week) and it's been awful. I have a very difficult class; yesterday for example we needed to evacuate the class because a pupil was throwing tables, this is just one of many incidents. My DS has started nursery and LOVES it but we have all been constantly sick for the last 2 months; it's been utterly miserable tbh.
Anyway, I feel like I'm on the edge right now. The stress of the last year is really getting to me; when DS turned 1 it brought up a lot of issues. Teaching feels just totally impossible right now; working full time does too, especially since we have all been so sick and have needed to take days off here and there. I'm very close to tears a lot of the time. I feel really low and overwhelmed by it all. We were trying to get a mortgage on a house, which needs to be in my name as DS has a poor credit rating, and we have a house lined up. I feel like the pressure is really on and I'm just not coping. I just want to leave teaching right away but I need to work 4 weeks notice regardless so it makes sense to stay until the summer just so I get the extra money for over the holidays. (I'm in Scotland so can leave any time) but I just don't know if I can do it. Another part of me also does want another baby at some point, and the logical move would be to stick in with both jobs and get pregnant quickly so I get decent mat leave pay. It would also mean that DS would be in full time childcare (a combo of nursery and family) so if I was as ill as last time I would know he was being looked after.
I just don't know what to do! I wish I could sign off just teaching and not the other job, as the other one is really very manageable and I'm really keen not to rock the boat in that role as I love the job. I just feel like I'm really close to falling apart!
What should I do? Any advice is welcome. Thank you!