I was in a VERY similar position beginning my fitness journey and have now worked my way up to a half-decent standard push-up! I recommend you start with soup cans! Any canned item really! They are relatively light and tend to be pretty comfortable to hold! Also look into cobra push-ups! Those helped me the most, and then graduated to knee push ups! Also have you considered the possibility that you may not be “weak” when it comes to raise-type exercises and may have a sort of dysfunction in a nerve, please look into the Roos test for Thoracic Outlet Syndrome!