He will throw himself back when he doesn't want to be put down or doesn't want to go to bed whatever it is, and slap and grab at my hands when i change his diaper... probably all normal but I can't figure out if just saying no is enough.

what does he do? maybe try the opposite of what u have been doing for example my baby is a month old & cries so much, i always went to her rescue as soon as i heard her or picked her up to calm her down. me & my husband decided no more & just let her cry now she just calms down & goes to sleep instead.