Is this my mucus plug ?

So I’m 24 weeks, 5 days ago I woke up with a tightness in my stomach and back along with pressure.. It lasted on and off for 1 hr where I couldn’t even sleep. It definitely didn’t feel like Braxton Hicks I usually had. So, I to the doctor when this first started and she brushed it off and tried to make it seem like I was delusional when I told her I think I may be trying to go into preterm labor. Yesterday I rushed to the the hospital because it came back . They told me I was slightly dilated , my heart was beating irregular and I had slight fever. I was monitored and eventually everything got better after I was given treatment . This morning this white mucus strand with a brown stripe fell out. Could this be my mucus plug?