At 29 weeks, some tightening is normal (Braxton Hicks contractions lah), but since you're also getting period-like cramps and backache, best check with your doctor or midwife just to be safe, these things can be normal pregnancy stuff, but they'll want to rule out anything else and give you peace of mind. A few of us preggie mums in my group had similar sensations around this time and it turned out fine, but honestly, better to get checked out than worry, especially since you're mentioning pain on top of the hardening.