Hi teresa, firstly congrats on your bubba!

From memory there is a wonder week around the 10 week mark so perhaps that is contributing (have you heard of wonder weeks? they are developmental milestones and occur at pretty predictable times, with side effects such as clinginess poor sleep etc...google it)

Otherwise, it is pretty normal for babies to want to be in a parents arms. Do you have a sling? They really are a life saver, and you can go about your usual activities with them comfy and close.

It is also normal for bub to be clingy if they are getting a little cold, or perhaps a new environment - even the change of the weather!

I doubt your MIL holding the baby has really contributed, as babies don't really know routines and habits (imo anyway) until well after 12 weeks. I know it is frustrating when things suddenly stop working, but unfortunately (and sometimes fortunately) babies change so quickly, so that as soon as you're onto something good, they change again (which also means the bad times pass too!)

I have metamorphised so many times since dd was born. Cosleeping, self settling, rocking to sleep, feeding to sleep. We have done it all at different stages. Try and go with it if you can. It all goes so quickly!

Also, please remember there is no such thing as bad habits...you are doing the best you can with a little human, and some of these little humans are more demanding than others (I wish someone had warned me my child would be more stubborn than me!)

you're doing a grat job!