No mucus plug, but very crappy and slight back ache 38+6

Zee

Today for the past 2 ish hours I’ve been having pretty good cramping on and off. My back has also been aching but not very often. Could this be the start of labour or something else. I’ve noticed a lot of tummy tightness (also on and off) but I’m assuming they’re Braxton hicks because they aren’t painful. Ftm at 38+6 but haven’t lost my mucus plug.