Just because it's big does NOT mean it's always melanoma
. And just like the person above me said, sometimes even the ugliest ones come out just fine.
I have one on my torso actually that is a bit big, about 6mm. It's been there as long as I can remember (maybe 3-5 years?), never has changed but it just kinda bugged me it was bigger than the ones around it. Years later, after scaring myself by looking at melanoma on the internet, I was convinced it was melanoma, even though it really didn't look that strange.
I went to the derm, showed it to her and she said even though it's a bit big, it looks just like the ones around it (and it does, the other ones are just a bit smaller), so there was nothing to worry about. She actually took one off my back that I guess (never noticed it) that had a white ring around it and varied in color. Came back just fine.
I also had two moles I was concerned about that I had removed recently also. One was a bit odd in shape and the other one looked a bit ragged in border and had color variation .. again
came back fine.
You have to remember that melanoma is VERY rare. Your mole might have changed because of your pregnancy - I have heard of that happening because of all the hormones in your body. You'll be okay, I'm sure of it!