Oh Asia, I totally understand this. Its the same every year, and just reminds me more and more that I don't have a nice Mother.
Every year I try and pick out a card for her and go for the one that is least 'mushy'. I read ones that are like 'you are the best mum' or 'You are my everything' etc...and I try and find the ones that say "You are my Mother, there isn't anything I can do about that".

I just (literally 30mins ago) picked out a card for her that says "It's Mothering Sunday, wishing you the best". It's the best I can do.

Meanwhile, all of my friends are posting about how wonderful their Mums are etc etc....it hurts