Bleeding-28 weeks

So I'm 28 weeks with fraternal twins and I woke up this morning with some bright red spotting. I called my dr and of course it took me to an automated system with another dr's office and they never called back. Both twins are still moving and the spotting has stopped, but I wanted to see if anyone else experienced this and what happened. I'm afraid it could be preterm labor because I also have gestational diabetes. Thank you!