If you keep a dose of Plan B in your medicine cabinet where you can find it immediately should a condom fail, condom use can be perfectly safe.
Good condom use techniques can aso help considerably. Inspect the condom after sex for tearing, an he should stop when he feels the condom tighten around his head. That is a sure sign it is going to fail and according to Durex's research almost always happen before failure.
Other than this, all I can suggest is trying the other types of pills. Every woman reacts differently, and your side effects can even differ from time to time, even if you go back on the same pill that worked for you previously.
Best of luck!