Staying with in-laws

My first born child is now 2 months plus. I am staying with my in-laws. They are kind to me and also adore my son very much as he is the first grandson to them. I have some arguments with my FIL previously as we have different views. He likes to carry my son for very long hours (2-3 hours) and always claim that he will definitely cry if he put him down. After much efforts I put in, my son now can sit on rocker/play on gym mat for 10-15 mins and also sleep on baby cot at night most of the times. He then said words like “eh, why he is not crying anymore?” whenever my son sit or play by himself. Now I feel possessive and hesitate to seek help from my in-laws. I even feel annoyed when they insisted to help me on something after I rejected them gently. On the other hand, I blame myself for having all these negative thoughts towards them.