my female vield

this is my female vield. i have had her since she was a baby. i think she is pregnat, but she is not showung the "gravid" colors. but i have heard of females doing this before. she has been showing black streaks,and she has been getting slowly but surely heavier (this is what led me to bleive she might be gravid), but that is it. so if you could please help me, and if she looks to you like she might be pregnat, let me know.