Maybe both things are true. Perhaps both sides have been dominating forces in your life and they are clashing with each other because of it with you in the middle.
I know what you mean by going along with someone for an easier life. If someone has a fussy, fretty anxious partner who is always getting a microscope put to look at fine detail, then yes, sometimes it's easier to just do what they want than argue.
Your partner might just me more anxious than usual, as he is not only getting used to his own parenting skills but yours too. Your parents might be capitalising on what they've seen in order to make you doubt him.
Sometimes, a certain type of person will end up infantilising you by saying they just want the best for you with this type of micro managing (what they sometimes want to say is that only they know what's best). As begnign as it might come out in their tone, what it means is 'I think of you as being like a child who can't take care of themselves, or someone who is too dumb to do so, so you really need to do what I tell you'.
What I would do is get used to say 'no'. A gentle, firm, persistent 'no'. Make your case in a sentence or two, but do not be dragged into arguments about your mothering choices. See how he reacts and keep saying no more often to all sorts of things. For example, if he wants you to hurry up doing something and you are not finished yet, just pause for a second and listen to what YOU want to do. Start honouring that a bit more.
If there are concerns about your weight or nutrition, keep in contact with your healthworker or GP and ask them what your weight should be and about your current diet. Don't discuss it with any one else for now.
Don't alientate yourself away from your parents. You need all the support you can get right now.