I finally got the ultrasound done on my legs today.  With a PE the concern is that the clot in the lungs originated in the legs.  The ultrasound of my right leg was clean and clear, but my left leg has a clot (fairly sizable) so no exercise for me for now.  The Xarellto is the preferred drug to disolve / breakup the clots, so I am already on the correct medication.

A quick google search yielded this article

https://www.webmd.com/cancer/news/20081118/cancer-drug-avastin-raises-blood-clot-risk

which shows that the drug Avastin (which I started taking at treatment 2) has as a potential side effect an increased risk for blod clots, in particular DVT, so at least we have a probable cause.  Since I need that drug as part of my treatment regime, I expect to stay on the Xarellto for the duration of my chemotherapy. At least this explains why my left leg has been so sore.  For now I will continue the medication and increase my hydration (which to be honest I have not been paying as much attention to as I should) since I know historically that my blood becomes noticeably sludgy when I am not fully hydrated.  So no more can I claim to have avoided the chemo side effects.