Well Kyogagirl64 I must say it is refreshing to see someone post and then dillegently repost.
You obviously are serious and interested in helpful responses. Very soon I imagine inner athlete and others will mindfully respond. So let us anticipate their level of detail and due diligence as they can be a wealth of help.
Please consider adding some detail to your report of back pain/strain. Location or proximity, likely cause of injury, poses that make it feel better or worse. Professional evaluation would be best and hopefully your Dr. can put you on the right path. Get details since if you can’t afford a physiotherapist, you may be able to find on-line enough support path to self healing. Maxims like
Rest, ice acute pain, heat and gently approach discomfort. Avoid advance poses til you are acute pain free, stretch and build muscle that may support structures and assist the reduction of chronic pain.
Tight pelvis is a good start and there are poses you can look up to open the pelvis for sure, but do any of these increase the back strain? Yoga should heal and not hurt, so yes have the patience to work mindfully towards your improved self.
3 months is hardly a long time, to see gains in any fitness regime, or mindful practice.
Celebrate though because it is a great foundation laid down now for you to build upon.
Your body will continue to adapt, poses that escape you will be approachable. The many other wonders of Yoga will open to you like petals of a lotus.
Namaste