I really need help

I recently broke up with my ex gf of 8 years and met someone else, The first time we slept in the same bed i wanted to start touching her but i could feel like i wasnt getting erected but thank God she stopped me because she didnt want to rush the sex, due to the fact i didnt get aroused i made sure i bought over the counter penis pills at the gas station which worked the first time we had sex 2x, it wasnt until the next encounter without pills i experienced my first ever loss of an erection which has been a nightmare ever since we have been together 5 months now and sometimes i get erections, sometimes i get erections and i ejaculate in 5 seconds, sometimes i get erected and while im penetrating it goes down and sometimes i dont get erected at all. So i decided to have sex with my ex and it was amazing in a matter of 2 days we had sex 8x while with my new partner im having trouble having sex 1-2x without any erection loss. Please i need help