Engine light comes on

I own a 1997 mazda millenia, mileage 130,779, 6 cylinders. I purchased it used about 2 years ago and throughout my ownership, the engine light would come on now and then and go off in a few days. The car was running great, so I didn't worry. I used to work at a car rental place and the check engine lights would come on when it needed to be serviced, so that's what I thought was wrong with mine. Well, I noticed it was hesitating a bit when I would press on the gas and then last week, I was pulling into a parking lot when it started idling really rough and it died in the parking space. I tried starting it again and it wouldn't turn over. After an hour, I went back to the car and it started, but it was running really rough. I checked the oil and it was low, so I bought 2 quarts. I put one in and it was still low so I put the other in. I also put some injection cleaner in the gas tank hoping that's what it needed. I strarted the car and waited until the oil circulated and then drove back to work. It was fine for until yesturday when I could feel it hesitating again. I put more injection cleaner in the tank and drove home. It drove great. This morning I could tell it was hesitating a little and when I was waiting to turn left, it died. I got it cranked, but had to keep one foot on the gas and the brake. I parked it and then the engine light started flashing at me and then went solid staying on. What's wrong with the car?