If, as you say, there is the likelihood of a bad reaction between Sertraline and Propranol, then don't take them both. I was prescribed Propranol with Effexor, because of bad anxiety, and there was no reaction between those two. However I did have a bad reaction between an anti-depressant (can't remember which) and migraleave for migraines. I had a bad fit.
Yes your BP is high, but it is really up to you what you do. Propanolol is a beta-blocker to slow heart rate.
I found once my anti-depressant (Effexor) kicked in, I did not need the Propanolol. I just took it for a short time. The body may have bad reactions at first, to all this medication, but should adjust with a few weeks. Up to you. Have you discussed your worries with the psychiatrist. Phone and discuss. Sertraline is an anti8-depressant, so it would seem you have depression as well as anxiety. They usually go hand in hand.
I am so sorry you are going through so much at the moment. Things WILL get better. Just give it a bit more time. Try taking the medications together, and see how you go.
I have taken Propanolol and Effexor for a couple of years with no issues. I don't take the Propanolol for anxiety but for a tremor in my hand. Propanolol is used as an anxiety medication, cluster headaches, high BP and tremors like mine. I have taken it with just about every antidepressant out there with no issues. At one time I also took a BP medication with it due to high BP and with no problems. Although with lifestyle changes I was able to get off of the BP medication. Pharamcists will not fill a presciption that will interact with the other, they will call your doctor. You can call your pharmacist and ask him about the two medications, they are most knowlegeable when it comes to drug interactions. Take care.