Is My Fish Pregnant?!

[epicleahhhx]

I just got some fish yesterday. I think they're platys. 2 of them are long and thin and I'm pretty sure they're males. And one is shorter and round. So I know she's a female, but she looks pregnant! I know platys are livebearers so they give birth to young and not eggs, but one of the males keeps chasing her and ramming into her. Only fish who lay eggs do that. So here's a picture, is she pregnant? And should Iput her in a separate tank if she is away from the male?

 

[Paradise3]

No picture?
 
To sex them look at their anal fins. These pictures are of guppies not platies but it's exactly the same for all common livebearers(guppies, mollies, platies, swordtails and endlers)
 
Female.

 
Male.

 

[GetItSahn]

If you plan on keeping your current fish, you need at least 3 more females but 5 would be best. The fish need a 3:1 female to male ratio so the girls don't get stressed and chased to death

 

[KrystaK]

Being a live bearer, she is probably pregnant. Live bearer females give birth monthly (give or take a week) in ideal conditions. They drop 5-20+ fry depending on the size and age of the female. 
The males will be paying attention to her because she is a female, it doesn't matter to them if she is already pregnant or not. With platys (As I recall, I may be wrong) females can hold sperm, and impregnate themselves at a later date. So your female may be alone for a few months and still mysteriously become pregnant. 
 
So if you think she is indeed a she then I would agree with the person above, get at least 2-3 more females if there is enough room in the tank.Unless you want to start up a whole new tank for her and any fry then there is no point in doing so. If anything, re-home one of the males and get one or two more females.