Painful sex: Any tips on how to have sex without pain?

I know that sex is supposed to hurt the first time, but it’s almost more painful than my periods every single time I have sex?? My first time was horrible it felt like my insides were bruised and my waist line swelled and became painful to touch. I later figured out that I’m allergic to latex!! Not only that but I have every symptom of endometriosis?! Sex is incredibly painful how can I make it less painful?