You could investigate fertility awareness based methods or simply the pull-out method, both in addition to condoms (I realize alone these are terrible methods of birth control, but combined with a condom, I think they're fairly effective). Also make sure you're using condoms correctly -- putting it on before his penis comes near you, leaving space at the end for the sperm to go, coming out right after, etc, etc, etc. I would be wary about spermicide because I've heard it can cause problems, like sores which would aid the spread of STIs.

Here's the Planned Parenthood Birth Control Chart. Maybe that will be of some help:

Birth Control Chart

On a side note, I've never had any weight issues with birth control, and I also think different types of pills will react differently with each person (just like regular meds.. some people have this side affect, others have that one).

Here's a link to something on PP that helps you pick which type of birth control is right for you:

My Method - Choosing Birth Control Methods

And good for you for wanting a backup method, being aware of side affects, and proactive in finding information!