Welcome to the forum!
OK, quick wins to get you going
Sating Pyjamas! (Long sleeve, Long Legs) they will help her tot slide about in bed a little better, you'll be able yo get an arm under her more easily, and trust me, boobs feel awesome under Satin!
If you dont like Satin (I find it to hot and sticky in summer) then any PJ's will do, but she wont slip over the bed sheets as easily.
White or a very light pink for preference in colour to avoid any risk of staining.
You'll get used tot he weight, it takes time. It's not like carrying a sack of spuds or being able to press xyz down the Gym. this is a human sized and shaped lump that wobbles about and doenst help you at all! Take is slow, and you'll be fine
K