I too suffer from AFig, but I'm an old guy and lots of us due. Mine may have been caused by a leaky mitral heart valve, which was repaired about a year ago.
I underwent a procedure called Electrocardio version (no-intrusive other than for electricity) 8 days ago and now have regular sinus and heart rates, low 60s when at rest.
BetaBlockers, Toprol in my case, taken because my heart rate was high with afib, hard to say exactly what that means and there were so many false beats in the artial, but I hope to get off Toprol on my next follow up with my cardiologist. I too suffer from some shortness of breat and dizziness, due again to Toprol and the resulting low blood pressure. I am "blessed" with good/normal blood pressure, so the lower blood pressure is an unwanted side-effect of Toprol for me.
Feeling tired is common with beta blockers. I felt like I could take a nap a couple of times a day. The other symptoms you are experiencing seem unusual to me, especially the shortness of breath. These issues need to be discussed with your doctor. If you are not seeing a cardiologist, then you might ask for a referral.
Like Bromley wrote, there are things to do for a fib other than medication. In my own situation, I chose ablation, which was successful. Of course, these are also issues to discuss with your physician.
Sorry to hear about this. My understanding is that the prevalence of afib among people increases with age. The number of people who eventually end up with it in later life is actually quite significant. The good news is that there are permanent cures presently available, and new cures coming out all the time. It is good that you have this diagnosed; that was the hard part. I think you need to go see an electrophysiologist about this to discuss your treatment options. They will probably want you to work with drug treatments for a while before trying ablation.
As for the symptoms you are feeling, I think you need to figure out how to recognize symptoms of afib, and to distiguish them from other arrythmias, if there are other arrythmias present. The electrophysiologist can help you with this by giving you a heart monitor and some advice.