progesterone injections/vag supp question

Hey girls!  So I'm 35 just had second MC (first was last year at 13 weeks second just happened this month at 7 weeks) I have 1 21 month old boy. So we have absolutely no trouble conceiving. Our issue seems to be after conception keeping the baby. Has anyone has positive outcomes with taking either progesterone vaginal suppositories or injections? My OB said that generally after 3 consecuative MC they start to do all the testing to see what's going on..... but he told I can try progesterone next time I get a positive. What do you. Think? Any experience with this? TIA!!!!!!!!!