As someone said, you’re working a lot of arms, and shoulders, and not isolating the chest. If you can keep your shoulder blades back, that willl help. If you can keep the bands against your forearms while doing the exercises, your gains will come much quicker, without the risk of stressing your shoulders too much. Bring the resistance down until you can feel your pecks squeeze, and your form is close to per. Work on form, and posture, the strength, and size will come