have I got an STI???

Recently I have developed a stinging/itchy Vagina, it hurts when I pee & wipe, there's no marks but quite a lot of redness anywhere where it stings. I have a white spotty discharge occasionally and have had unprotected sex. I'm unsure what this is could be someone please help?! I had just also started using Sented liners so I thought maybe this had caused an infection as I have sensitive skin, I've stopped using them now but it's still there. Could someone give me some helpful advice as to whether I should get this checked out or not??