Am i buying the wrong Tank Tops?

So ive recently gotten some Tank Tops Online (bought like 4 in Total 2 from each Brand because i wanted to test out some Oversized tbh as well >.>) and ive been very Happy with them so far ^^

Sadly the only Thing that ive noticed and is very annoying is that they act more like Undershirts basically >.>
\ As in were talking about them darkening and also especially showing my Nippels as im not a Fan of Bras really which sucks :(

Like all i want is a Oversized Tank Top in White to combine with my Shorts :(
\ Is it because im too Fat still and if i go thinner it shouldnt push as hard to the Fabric or what am i buying wrong? :(

Theyre 100% Cotton btw so i dont think its due to the Material >.>
\ Theyre just very "Thin" Color Wise which sucks as especially and the Pictures they show no Skin of the Model at all :(

The Model was White tho and while i wouldnt consider myself Latino i am slighty more "Latin" looking atleast from what my Latin AMerian Friend tells me due to me being Italian >.>

If anyone has Tips please tell me as itd love to get some Cool Tank Tops which arent Ass and expose my Chest ^^"