I had exactly the same done as you and experienced exactly the same thing as you are now.
At around 2 weeks I began using powder adhesive as by around a week and a half after extractions the front of my plate was wobbling around.
My dentist had told me that a reline would be 2 years away.
(A reline is where they take another impression and then alter your plate to fit better).
I haven't even been able to go back for a check up or anything since I had my immediate denture fitted back at the end of November last year.
By about 2 months of using powder adhesive I had to move on to Fixodent which is now becoming ridiculous to use.
I did have a check up booked for April and when I booked it I told them I really needed a reline - they told me I would be able to 'talk' about a reline.
A few weeks before that check up they called me as my dentist had to cancel as he is going to a conference.
I rebooked for May instead. I also said I still wanted to discuss a reline - my partial just does not stay in at all any longer without a lot of adhesive - they took me seriously this time and when I have my check up I am having a reline as well.
The first 6 months to 2 years is when you will experience the majority of gum shrinkage.
By the time I get my reline I will be just under 6 months in to having my immediate denture.
It hasn't been the easiest time and some days have been a struggle if I haven't added enough adhesive, at the stage I am at now I am finding eating and speaking becoming more difficult - BUT - the gum shrink I had at say 3 months to what it is now I am glad that I have waited and dealt with things as best I could.
My partial fitted so totally perfectly right at the start, then I had a couple of days of feeling swollen and after that was when I started catching my lip just like you are. The adhesive I used back then helped secure the front to the extent where my lip didn't catch anywhere near as much.
Part of it I think is having to get yourself through the plate feeling losse times and doing the best you can with products you can buy to help.
Especially if your dentist won't help - but to be honest - and as I said I am glad I waited - but I just wish the date for the reline would hurry up now!
But yeah, for now get in a bottle of some powder adhesive I used Polygrip Wertners and in the early stages just like you are it hugely helped. Had I already had some in at a week and a half post extractions I would have used it but I had to wait a couple of days to get to a shop - by then I really needed it!