does anyone know how to morph someone pregnant? i would like to start myself but dont know where to start.

https://preggophilia.com/my-morph-method-t

Here's an old post of mine that will help if you have photoshop. ( This is only for enlarging currently pregnant bellies)

Does that apply when the girl isn't pregnant?

It is more difficult to add a pregnant belly to a non-pregnant girl than it is to morph an already pregnant belly to be larger. I use Giimp2.8 which is free to download. Download it then you will need to play around with it to learn how to use it. I may make a tutorial sometime, but it will take me a while to get around to it. So once you have Gimp2.8 and have some idea how to use it, you can make a girl look pregnant two different ways:

1) Duplicate the base image, then stretch her flat belly to look pregnant. On the warped image, apply a layer mask and erase the distorted background behind her belly. FWIW this is the exact same method you would use to expand an already pregnant belly. You likely be limited in belly size this way since a flat belly will quickly look distorted when you stretch it.

2) Transplant a pregnant belly from another image to the girl you want to morph. You first have to find a pregnant girl posed in the same way as your subject and with similar skin color and lighting. Open that image and select and copy her belly (just a box or circle selection is fine, you will cut off the excess later). The open the image of the girl you want to look pregnant and go to 'Paste as new layer' under the 'Edit' tab. Then position and resize the belly to fit. You may also need to work the color, brightness and contrast to make the skin match as close as possible. Then apply a layer mask to the belly and erase all the extra background and trim it to fit your girl.

That explains how the 3 pictures you made about a few I gave you like a long time now, were impressive, despite being simple as a bikini, and jeans with blouses. But what about if the girl is wearing a dress? Same procedure to adjust the belly?

If she is wearing a dress you probably just have to use method 1 (warp). It will look distorted but you may be able to paint in some texture.