Bleeding returned ?

I'm 4 weeks postpartum and hadn't bled for well over a week but now I'm bleeding again. It's s mixture of red, brown and tan looking and I can get by with just a super thin liner. It has a smell...I wouldn't say it's foul or even bad but it's definitely strange.  I'm also feeling weird...almost like a have a uti or I'm getting one but the pain is so mild and dull that I can't really pinpoint where it is. Should I be concerned?