I've had 2 sinus infections in my 15 (so far) weeks of pregnancy - I love having no immune system! I got straight onto the ABs - cat A so safe for preg - but there are two things that can help to temporarily ease the pain:

1) use a ceramic bowl, pour in about 3 cups boiling water and about 10ml eucalyptus oil - set a timer for 10 minutes (cos it feels like an eternity), sit yourself over the bowl and put a towel over your head making sure there are no gaps between towel and table. You'll cough and gag but try to breathe in through the nose. Can help if you're feeling a bit chesty too but can trigger off asthma so be careful.

2) get 8 camomile tea bags and soak in 1/2 cup boiling water for about 5 minutes. Get 2 facewashers and line up the drained tea bags along the middle of one of the towels. Fold this towel into thirds, overlapping the ends over the line of bags. Drizzle a little of the liquid over the towel, then wrap the second towel around the first towel. Lay this over your sinuses and forehead until it's cooled down. You can zap this in the microwave if you want to reuse it. Don't burn your face!

Hopefully you can get a bit of relief - sinus pain is awful!