starting to build muscle with a weak upper back?

This could be a dumb question but....

In the last 8 months i have lost 48lbs, im finally in the "healthy weight" bmi range and feeling great, Im really proud of myself, Ive been doing a small amount of jogging, and now on c25k w3d1. The problem is im flabby, i think i have another 10ish lbs to drop, currently 138lbs 5'4".

In the past i have done 30 day shred, pilates, and dumbells, everytime ive done any of these i have repeatedly hurt my upper back to the point it hurts constantly and i have to stop for 2 weeks! the last time I went to the doctors who advised me to avoid straining my back and just doing stretches.... the thing is, i would love to tone up my arms and get rid of my pouchy belly!

Does anyone have any advice on how i could do this without hurting myself again? Exersizes for the arms and abs? I dont so much want to be skinny, just toned!

Any advise would be really appretiated!

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