Dear Maam,
As a general physician with 3-4 years of my experience, I think I stand as an eligible person to address the problems you are facing.
To note, Most crucial points that you mentioned are:-
1) Left breast heaviness- Given your obstetric history, I think that’s totally normal because of lactational reasons. There is always a difference in feeding habits of instants and toddlers. Sometimes they feed more milk from one breast and feel satisfied with the hunger just after drinking few ounces from the other one. So due to incomplete emptying it may seem a bit heavier than the other one.
2) pain in left upper back:- That’s also completely normal if you are habituated sleeping facing a single direction as you mentioned earlier.
3) Pressing the painful area in upper back causes some sensations down the left hand- That happens because the nerve supply of upper back and the left arm and forearm are supplied from a single plexus of nerves called Brachial plexus. So it’s completely normal too.
The thing that is really important to note is that you are feeling pain in your upper back.
Next Steps
1) To relieve breast heaviness, try feeding your baby from the left breast first and then the right breast for few days.
2) for left upper back pain- Please improve your sleeping posture, that will alleviate further pain. And in addition to that you can take Pain medications prescribed on the basis of your clinical history that really suits you.
3) for the radiating pain to left hand, you don’t need to worry, that will go away if you practice changing your sleeping posture.
Health Tips
Though I have advised all the things, still I should remind you that just texting a problem doesn’t address the real problem , let aside solving the problem. So i would advise you to please consult verbally or on video call for a better understanding of your symptoms, so that i can treat accordingly.
Thank you. Have a good day.