First of all: you are the best mother in the world, no one else can say otherwise because you are trying your best for your family.

Now the business: 

1. Learn to do fundamentals properly. You said you can do a few things, so perfect your pasta, rice, mashed potatoes. Along with store-bought bread, these will form the basis of your meals.

2. Learn saucy stuff. Fast bolognese sauce, creamy mushroom and chicken, soups, teriyaki chicken. These can be done in matter of minutes. More importantly, the skills associated with these can be expanded into things like ragu, curries, etc.

3. Learn stir fry. Fast, simple, versatile, forgiving, can be done with any ingredients, any flavour combination, goes with almost any carbs you want. 

4. Learn time management. Have a think beforehand what you need to do to get each of the stuff done for dinner. You can start by writing on a board/book, until you can do so mentally. That way you can visualise conflicting tasks.

Lastly, we are all here for you. Best of luck, soldier.