Hi. I took those subjects as well, although I did them at college. I'm in a bit of a rush right now so will just write down some advice.
Because maths and further maths (and physics to some degree as well) are so connected, at some point it will all come together and the different subjects will begin helping each other out.
The subjects are pretty hard but if you generally enjoy doing maths it will be very doable.
Take a step back and think about what you are doing. I know how stressful studying can be (and I imagine self studying is worse), but in the greater scheme of things not understanding things here and there isn't the end of the world. When you don't get something, don't panic or stress, just laugh, try reading it again, look for other sources to explain it, try some questions or just say you'll have a look at it again later.
Get a lot of fresh air. Walk, jog, cycle. You don't wanna be inside all day.