How do I get better at handling my liquor when out drinking?

Hi, I’m a 20 year old guy (legal to drink where I live). I usually have 3-4 Coors Lights at home on my days off work and handle it fine. The other night I went out to a bar and had two Coors Lights in maybe an hour. I left the bar and didn’t feel good, ended up running into a department store and getting sick in their bathroom. Why do I get so drunk when I go to a bar but I’m fine to drink at my house?