You have only had them a week and a half. You gums are still healing... for about the next 6 months, so you are going to have some looseness at times.
I am at the 3 week mark here and what I have found is that Fixodent with Scope works well (very well) for me. I put a full thin line all the way around the top plate about 1/4 inch from the outside edge, then I let it sit for about 1 minute to 'set up' a little. Then, after rinsing my mouth with cold water, I put them in and press them in place (using the pad of my thumb on the center of the palate) and then I lightly bite down and hold them for another 30m seconds or so. They are IN there for the day and most of the night.
Mara is right about not eating immediately after putting them in. I usually wait at least 30 minutes so the adhesive can settle in and do its thing.
Try chewing on BOTH side of your mouth with your back teeth and avoid biting with your front teeth. When you bite with your front teeth, they tend to loosen some. I just started biting with my front teeth a few days ago and it was semi-soft stuff... not steak etc.
I went to Red Lobster last night with my daughter and had no problems eating anything. So, be patient and you will adapt. It takes time and practice.