Ok, WRose. This is absolutely the worst time for you. You are at home with two very small children. I can absolutely assure that things will NOT stay like this for ever (even tho god knows it feels like it when they're this age).
I remember my friend's (girls') school getting in a motivational speaker to speak to the A level students. This speaker said to the girls: "Yes, you CAN have it all, just not all at the same time". Which is very sound advice.
You had your children fairly young, which will turn out to be a wonderful boon later when you are still young enough to do really active things with them when they are 11 and 9, 15 and 13 etc.... They are changing all the time and they will not be toddlers for ever. The idea is to survive this stage, especially if you are not enjoying it.
The best thing to do would be for you to try to work what you want to be doing by the time they are both at school. There is a fair amount of childcare and other help available to you if you decide you want to go back to college for example. It might really lift your spirits to be doing something you enjoy alongside other grown-ups, and knowing that it is leading somewhere professionally and your children are being safely looked after.
Being a stay at home parent is a tough enough job at the best of times, far tougher if you are feeling down, unsupported and stuck in a rut. You actually have the power to make this change. You need something to look forward to- we all do.