Hi Angie
All is not lost. You can improve your pelvic floor muscles but like any other muscles you need to exercise them on a regular basis. Here is a couple of guides to help you.

Sit on a dining room type chair.
Spread your knees apart.
Lean forward so that you can feel your vulva touching the chair seat.
Now imagine that you have got diarrhoea and are not near a toilet.
Pull up your muscles in you bottom.
Hold your mules in that position.
Next try to lift your vulva of the chair seat by just using your pelvic floor muscles.
Hold that for 10 seconds.
Repeat this about 10 times.
You need to do this about 5 times a day.

First get to know what it feels like and how to do it.
When you go to the toilet (for a wee) try to stop the urine mid stream, and hold it for a few seconds. Try to do this 2 or 3 times each time you go to the toilet. After you have mastered this the next step is to not only stop the flow of urine but to pull the urine out of the toilet and back into your bladder (not for real). You can imagine how hard your muscles would have to pull up to do this and that is what you should aim for.
When you know what it feels like and how to do it. You should do the same thing throughout the day. A good idea would be to use a prompt to encourage and remind you to exercise. For example, exercise every time you sit down and before you get up again. After a few weeks you will be exercising without even thinking about it.

Also a little rhyme that may help you is:- Open a door do the pelvic floor.