This is a very vague question or statement am afraid
Going to have to ask for more information.
What size of tank do you have?
How long have you had these platies in your tank?
And lastly, will need some water information, namely need hard or soft water information?
You can get this from a test kit or from asking or searching online your local water board for local water information with pH as well.
whilst Ch4rlie is correct in needing a bit more information in general with any live bearing fish the answer to the questions is - if they've been with a male for around 6 months (this included their time at the fish store/breeder) then yes they'll be pregnant.
All livebearers (platies, mollies and guppies) can hold sperm for up to 6 months so even if you just buy females if they've been in a tank with a male before you bought them they can still be pregnant. Most female livebearers are pregnant when you buy them because the breeders and fish stores don't bother to seperate them into male - female groups and also when they are young it can be difficult to tell males and females apart. Some males take time to develop a definite gonopodium.
If you are concerned about bloating (and from my experience platies are incredibly greedy fish) you can feed them some cooked peas. All you need to do it de-shell a cooked pea or two, squash the mushy bit between your fingers and add it to the tank. Cooked peas are great for constipation and a good healthy treat too