This may be accurate, but not for what you're describing. What you're describing is called agoraphobia. That's a condition of phobias that start spreading to more and more areas of our lives until, for some, they become afraid to leave the house. GAD is when you're just anxious all the time and scared all the time. Social anxiety is when you have a phobia to social situations, such as being with other people or going to events that other people are at. But the label isn't as important as the realization you have an anxiety disorder. There is a difference in treatment if you undergo therapy, which I would recommend, as the therapy for agoraphobia would be different than that for GAD or social anxiety, but there would also be some similarities. With medication, the same ones are used for all three with the exception of the propanolol, which is only usually helpful for social anxiety or public speaking fears. Because it affects the heart, if you do try it, make sure your psychiatrist explains it. My own feeling is, when you're just starting medication, and I think with your condition having progressed this far you do probably need it to calm you down enough to go to therapy, the best thing is to try one first and see if just one works. That one would be the Zoloft, which can be very effective. If it works, you only have to deal with one medication. If it works but not quite well enough, you can add something. If it doesn't work at all, there's no reason to take it at all and you would taper off of it as slowly as you need to and try a different main medication, which would usually be an antidepressant like Zoloft.
Agoraphobia is an anxiety disorder that falls under general anxiety disorder. So GAD is at the top and agoraphobia is under it. Most doctors do indeed treat for GAD if someone has agoraphobia and that is important because the point is to get you well. A lot of people with agoraphobia also have panic disorder. Here's information on it to read through that I think is helpful. https://www.mayoclinic.org/diseases-conditions/agoraphobia/symptoms-causes/syc-20355987 When I read things like this though, I also know that each person is different and have their own unique experience with the disorder as well as treatment.
Probably one of the most important components to treating agoraphobia and panic is psychotherapy. Do you see a good psychologist as well?
Zoloft and other antidepressants are often prescribed. Since you just started it and already have anxiety, I know it is hard. But the thing to remember is that your body has to get used to the medication and that takes a little bit of time. These types of drugs have 'start up' side effects. These come on early but then go away. That's possibly the drowsiness or nausea you are mentioning. Give it some time to see. It takes about 6 to 8 weeks for Zoloft to work. And Zoloft is a good drug but the thing about that one in particular is that there may be some trial time to get the right dose. It does tend to take a higher dose for effectiveness than the starting dose. Also (I keep thinking of things to add, lol) with antidepressants like Zoloft, it may help to start low and raise the dose slowly. Tapering up. You'd want to do this exact thing if you stop the medication, taper back down on the dose slowly. Hopefully your doctor is guiding you appropriately. But give this some time and hopefully the Zoloft will help.
Combining medications is very common for psychiatrists these days. Propranolol is used for panic and anxiety. It's a non selective beta blocker that prevents adrenaline from building in different body areas including the autonomic nervous system. By blocking the effects of adrenaline on these receptors, the autonomic (physical) symptoms of anxiety/panic are typically reduced.
I can't really read anything in what you've written to think you've been given bad medical advice and think those are two commonly used medications to treat what you've been diagnosed with.