Car Overheating

It possibly could have a bad head gasket or other serious issue with the engine. Has it been losing coolant?

Sounds like a coolant leak, and you where low on coolant. Let it cool down, and check the coolant level, fill if necessary. Hope you don't have to go far to the appointment. Check the oil also.

The mechanic put antifreeze in there three weeks ago when the replaced the other things, I don't know how to check for coolant ( I don't know a lot about cars)

My 02 Focus SE sedan would overheat at speeds above 45mph with the temperature gauge inching up toward the red. I got off the highway right away so no damage. It was fine at city speeds under 40. Searching online forums revealed many owners of this model have similar issues. Had my cooling system flushed and filled which didn't actually help, kept an eye the coolant level and was contemplating if replacing the radiator was worth the cost however, it turned out to be a hairline fracture of the coolant reservoir line. Once the reservoir and the lead-in tubing were replaced, the problem resolved and my car has driven just fine, even on the highway. That was two years ago and (knock wood) things are fine. Ask your mechanic to pressure test the cooling system, see if that turns up anything. Also, Betty, one woman to another - you owe it to yourself to get under the hood and learn what things are. Every women should learn how to check her own oil level, check the coolant and power steering fluid levels, refill the windshield fluid, and and know how to fill her tires with air. It looks scary at first, but it's not that hard to figure out. Seriously, prop up the hood, get a flashlight to help you see, and open the owner's manual to the diagram of the engine. Let it guide you to the location of each dipstick and gauge. Tinker around a bit, see how things fit. You can't break anything just looking. If it still doesn't make sense, recruit someone with car knowledge to step you through and teach you. You will feel so much stronger and powerful with a little knowledge under your belt. You will save money by doing things yourself instead of paying someone else. You will feel more secure before a journey knowing that you have checked fluids and prepped your vehicle. And repair people tend to respect you more. We are women - nothing should hold us back! Good luck with your coolant issue.