Birth Control as needed...

Okay so... I've had the implanon. It was great at preventing pregnancy but otherwise messed up my body quite a bit at the beginning and end of treatment. So here's the deal, I go to my boyfriend's once a week and spend the night, we have sex 1-4 times. I would like birth control other than the withdrawal method and condoms are a no go. Between his size and my latex allergy, even the custom websites can't make the right condoms for us. I don't want to take a pill every day when I only need to prevent pregnancy once a week. I've heard of IUD risks and and not really into all that. What are my options? I've only ever been on the implanon. Any input is appreciated.