All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. {C}
The fear that you have is not necessarily due to magic; it might be due to a psychological disease. Therefore, you should consult some trustworthy psychologists.
However, your illness is also likely to be due to magic and the like, but it is not permissible for anyone to accuse your mother-in-law of having done magic to you without evidence. The so called Shaykhs who informed you that she did magic to you can not give certainty in a very serious matter like magic. Allaah Says (what means): {O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin.}[Quran 49:12] In principle a Muslim is innocent unless the contrary is proven against him.
In any case, if you predominantly think that you are affected by magic, then its treatment is easy, Allaah willing. Jaabir narrated that the Prophet said: “For each disease there is a cure, and when the (right) treatment is given, the disease is cured by the Will of Allaah.” [Muslim]
For more benefit, please refer to Fataawa 82918 and 84806.
Therefore, you should be keen on performing good deeds and avoiding committing sins. You should also supplicate and recite the Quran as much as possible, and recite the mention of Allaah especially every morning and evening. For more benefit on Ruqyah, please refer to Fataawa 88705 and 85500.
We ask Allaah to cure you and bless you with good health.
Allaah Knows best.