I was in very similar circumstances at age 20.
Married, working a full time job cutting frozen chicken on second shift 40+ hrs a week making $7.50 an hour with a wife who didn't work. I was taking a full class load (18 hrs) in chemical engineering, $250/month rent, $250 truck payment, $250 phone bill (wife loved to talk to her friends since she wasn't working - biggest mistake I made was not putting a stop to that but young and in love you do stupid things) and the rest was spent on utilities, food, gas, etc. College was paid for by scholarships that required a 3.0 GPA so no slacking allowed.
Luckily I had been taught by my parents that if you want something, you work for it. I spent 6 years getting my degree, worked full time all but the final semester. Had a son during college as well. Took on roommates at times to help with rent, bills, etc. Worked two part time jobs, co-oped two years.
You decide your attitude. You control your reactions. Be responsible. Accept that things aren't the way you want them today. That's your starting point. Decide what you out of life and start working working toward it. Your parents don't owe you anything. At 19, you should be paying a good portion of your way. The lessons you learn as this age will set you apart from many of your peers when you go to apply for a job after college.
Use this to your advantage. You are being given a gift of tough times. Show your character by how you respond to it. That is what determines where you go in life.