Assalaam aleykum ,
All praises and glory be to our Rabb the most high. In the Name of Allah the most compassionate the most merciful.
With the help and will of Allah may your health be restored
Sister , i would first advise you to make salaah. By Allah , i also had a decrease in my Imaan ,not so long back ,but Alhamdulillah ...i listened to a few lectures and was to told to remember death as i remember breathing.
I do this and had a rapid increase in Imaan because AstaghfirAllah, i am not ready to be questioned by my Lord the most high but i have to be prepared for it Alhamdulillah.
I have also read on topics such as Qiyamah and Jahannam ...these have also increased my Imaan.
And remember your illness is not a punishment rather it's a mercy unto you because the difficulties in this life decrease difficulties of the hereafter
In shaa Allah , we all will Attain Jannah at it's highest level
Ameen ya rabb