wonderwhy7

Recently purchased honda civic. Only had it for short time and decided to take it on road trip. 20 min on the highway the check engine light came on and within 5 mins of that the car felt like it got heavy if that makes sense. The rpm's were normal but the car began slowing down, all the way to 40mph, even with me putting the pedal to the ground. I pulled over, shut it off and checked it for leaks and everything. Found no obvious problems. Got back in started going again and it wouldn't let me go faster than 45mph. So got off highway and road back going 45-50(for acouple min). This whole time the temperature gauge never went past the halfway point, just so you know. The next day I started it up, check engine light still on, but when I went to drive it rode fine and the check engine light disappeared. Decided to go to autozone and have them check the codes anyways and came back with P1457, P1361 and P1362. Which looking them up don't describe the problem I had. Anyways the car had been driving fine on my usual routes which vary speedlimits between 30-60 and besides it getting alittle shaky when I hit 60 I haven't encountered that problem. The check engine light is still off. So acouple days ago I decided to test it on the highway again and sure enough, the same thing happened. 20 min in the check engine came on and the rest followed suit. I did the same thing, pull over for alittle and then get off the highway and return home but this time i couldnt get over 30mph. The next day the car was driving good again except it is now shifting hard getting into whatever gears are at 30mph and then again at 40mph(2nd and 3rd possibly- it is a 4cyl). Other than that it drives good. The check engine light went away driving it that next day and again still went to autozone and had them read me the codes and the same 3 codes as before came up. My BF says it is the transmission and I need to just get a new car but he isn't a car person and don't want to get rid of a car if there is possibly another problem that is causing this.

Sorry for the long response, I can answer any further questions if it helps you give me another diagnosis. Thank you for your time.