I've had strange upper back pain for the past almost 4 weeks. it's not extreme but just uncomfortable. almost like a soreness in the skin tissue and also a bit around the t4 vertebrae. i'm a bit concern if it's heart related?

Unlikely heart related. Back ache is not uncommon, Improving your muscle strength and flexibility through regular exercise is needed for long term result. Any exercise will do, walking, jogging, cycling, treadmill, elliptical etc. Start at an intensity that is tolerated and gradually increase the time and intensity of exercise to induce sweat. Exercise at least 150 minute/weem. Drink more water.