There are several possibilities.
Yes, short bundle branch blocks are possible. This will usually happen with changes in heart rate (often with increased heart rate) and as far as I know usually do not cause symptoms.
Another possibility is that you went into what is known as AIVR (accelerated idioventricular rhythm) which is a rhythm that origin in the ventricles, but at a rate similar to normal sinus rhythm (a slow ventricular tachycardia). That will often cause symptoms, but also usually (but not necessarily) change the QRS axis significantly.
Atrial arrhytmias will usually not change the QRS duration (except irregular rhythms where the interval between beats vary, like A-fib and PACs).
Your question is almost impossible to answer, and of course, technical problems may also be to blame, but again, this would not cause any symptoms. It all sounds a little weird, and if you have those symptoms occationally, it may be a good idea to investigate them. Ask your doctor.
Yes, I would say if they continue to happen you should go get an event monitor to catch it. Have you by any chance had the svt treated? I know afib and flutter can be hard to treat but some svts are quite easy to fix with an ablation. If you have frequent svt episodes it could be making your other heart issues worse and if you get it fixed it might help give your heart a little breathing room. Well, just asking. It sounds like you have a lot to deal with. Take care and I hope you feel better soon.
Thanks for the answers people.
Michelle, yeah actually I have an appointment at the Ross Heart Hospital at Ohio State University coming up. An electrophysiologist there is going to do an EP study and ablation if needed. I'm going to tell him about it. I don't know what all they look at when doing an EP study but hopefully he will be able to see most of what is wrong in there.