Spotting and back pain at 28 weeks?

FTM here. I'm currently 28 weeks and 1 day pregnant, due January 21st. For the past week I've had random contractions and they've hurt so bad they knock the wind out of me. Well a couple hours ago when I went to the bathroom I had some very light spotting. I called my on-call midwife and she said spotting during this stage is very common. But now I'm spotting and have had a couple of contractions in the past 30 minutes. I've tried calling midwife twice now but she hasn't picked up. Any thoughts or suggestions as to what I should do?