preterm labor???

Ladies please help me out! I'm due in January and I'm only 26 weeks pregnant but yesterday I lost what looked like my mucus plug (looked like the mucus plug I lost with my first baby at 39 weeks). This morning I'm feeling lower back pain and tightness and pressure in my lower abdomen. Should I be alarmed? I'm pretty scared and I'm just wanting to know if this is something I should be worried about. I had a c section with my last baby so if I was to go into labor I really need to be at the hospital. Please help!