If for many years(before this year), i had lack of physical activity always. can i be at risk of suddenly developing myotonic muscular dystrophy? because well this year i feel so many uncomfy weird symptoms. and now wonder if i got this or not?

No. After many years is not a term I would expectg a 23 year old to use. :-). But you need to see someone who can talk to you, examine you and maybe even order some tests.

In the absence of genetic history, blood studies, and clinical examination, it is impossible to predict whether you are at risk for myotonic muscular dystrophy. Have no clue what you mean by lack of physical activity or "weird symptoms". Suggest an exam by your primary doctor and an appropriate referral if necessary.