Tried the start stop routine its not getting to far and we are both losing the patience

Try slowing down. Take your time. Adjust your technique

Try having him masturbate an hour or so before sex.

He should last longer the second time around.

If THAT doesn't work, make him bring you to orgasm BEFORE inserting his penis into your vagina.

It sounds like he is not happy all the way around if he is also fixated on enlarging his penis. In his mind, are the subjects related?

Because length of time is subjective, how long is he lasting?
How long are you both wanting intercourse to last?
Has he always had a problem or is it a recent development?
Has the problem gotten worse as he tries various 'natural' ways to enlarge his penis?

The OP is also pregnant, has chlamydia (from the ex) and not sure if the baby is the new boyfriends.

That may also play a large part in this.

The OP is also pregnant, has chlamydia (from the ex) and not sure if the baby is the new boyfriends.

That may also play a large part in this.

Thank you for reminding me of those details in the op's story.