Valve seals

After I had valve seals,tightened,oil leak disappeared,but oil/anti freeze,warning lights went on and loud noise started on right side.I took it back he said seals were fine,didn’t hear loud noise,it is 2 weeks later,noise very loud,check engine light on all the time.and the car shakes and stops if you stop for a red light,it literally shudders.Have I just lost my car?

To be honest, I cannot figure out what you’re talking about.
One cannot “tighten”? valve seals and they have nothing to do with the way a car runs unless the valve guides are worn out, the seal is not installed properly, and over time it could be possible for a spark plug to oil foul, which could then lead to rough running.

"There is no way a valve seal can cause a come and go noise, except under a very limited scenario, and even that is a stretch.
You did not state the type of car, engine, mileage, the type of noise (rattle, knock,) etc. but unless some clear details are provided you will not likely get much of an answer here.

The CEL light means the computer has detected a problem and set a trouble code. Get the code read at most any auto parts store, and let us know the type of car, make model, year, engine option, and the trouble codes, and we can help from there.

BTW, the problems you describe are not necessarily a blown engine, but could be just a bad component. Get the codes read so we can help better.

Are you sure you didn’t have your valves adjusted? Still need to know what make, model and year you have plus engine size. If you recieved a receipt from the mechanic that did the previous work what does it say was done to your car.

You need to have your CEL Codes pulled. Post the code numbers here and someone should be able to help you.