28 weeks 1 day w/Twins, protein in urine, anyone else have that?

I'm 28 weeks 1 day expecting twins, a boy & a girl, & I have two kids. I had my 28 weeks prenatal check up today, they babies heartbeats were great, & I have a ultrasound on Monday to see how their growth is. I had to do the 3 hour glucose test the other day because I failed the hour test. The doctor said my 3 hour glucose test came back perfect, so that's a relief. The only concern she had were that my iron is getting low, I have bad edema in my feet & ankles, & I have protein in my urine. I've heard about protein in your urine, but have never had it till now. She said she wants to keep a eye on it to make sure I don't develop preeclampsia. Has anyone else had/has this, & what happened?