Hello and hope you are doing well.
To avoid the allergic reactions, try to maintain an allergen-free environment. Substitute all synthetic and cool materials with cotton ones. Remove all dust-collecting household articles like carpets, bedspreads etc. Alternatively an allergy specialist may try to identify the offending allergen and try to desensitize you.
Hope this helped and do keep us posted.
I suffer from this too...as do my two and 16 year old sons.
The only other thing that you can do is to prop yourself up on many pillows at night and have a humidifier running by your bed.
Keep up with the sinus rinses and nasal sprays.
Someone also told me to lay on my stomach, but I find this just plugs me up and makes things worse...but it might work for you.
I sleep on my left side now, and use three pillows...I find this works for me.