Don't over exert yourself. Eat lot of proteins like cheese, soybean, tofu, porridge, sprouted black grams. Also instead of lifting weights first of all start doing push-ups and chin-ups to increase muscle strength.
Bachelor of Ayurvedic Medicines and Surgery(BAMS), Post Graduation Diploma in Emergency Medicines And Services(PGDEMS), MD - Alternate Medicine
Ayurveda, Ghaziabad
This is due to muscular weakness. Do limb exercises regularly. Start to lift light weight dumbwells. Apply ayurvedic oil like prasarini oil on your shoulders.