When "not feeling good" is a concern 3rd trimester

Kelly
I'm 32 weeks and just feel crummy today. I never feel 100% and I'm always tired but I haven't even felt like getting out of bed today. I got up thinking food would help but felt like I needed to lay down a few minutes later. I don't have a full on headache or dizziness but my head feels kind of "fuzzy" and I lost my balance when I sat back on my bed. What's the difference between "normal" "I'm 8 months pregnant and not feeling good" and "I'm 8 months pregnant and should call my doctor." I have an appointment on Monday so I don't want to call if it's not a problem...I don't feel great but it's not like I'm in excruciating pain.