I have sinus problems too! I use brauer sinus tablets they are safe during pregnancy and make sureI am taking my multi vitamins, I have noticed it gets worse when I forget them.

My back is getting sore this week too, I am 23 weeks so at the same stage as you last time I swam as much as I could and it really helped. I was saying to DH that he will have to watch DD a couple of nights a week so I could jump in the pool, unfortunately ours is too cold with the weather in
Melbourne so I have to pay to go instead.