Fainting during pregnancy

Adina • I`m 24 with a 2 year old boy and another on the way. Married for 3 yrs.
I took off work yesterday & today bc I was tired. I work in an office at a desk but I still have been tired for some reason. I'm a FTM & will be 27 weeks tomorrow. I thought I had been experiencing preterm symptoms because I lost my mucus plug last week, have been restless & antsy, will feel fluid leaking out of me(I have no infections) been really tired, sometimes my heart will randomly beat fast & I get lower back pain. Well today & yesterday I took off work bc I was tired. Today I ate pizza rolls, a Mountain Dew & was goin to eat some pears. I got up, got light headed, my ears started ringing & I fell out on the floor. My husband had to pick me up & put me on the bed. Either my iron is low, I'm not getting enough nutrients, or my blood sugar was low. Idk what's going on with me. Any idea? I'm calling my doctor tomorrow. My next appt is next week with my midwife. They're aware of me thinking I lost my mucus plug the previous week.