Is your bump getting hard on one side? If it is then it'll be the baby pressing against your bump making it feel hard :)
I had contractions only on right side . I didnt feel contractions in my stomach though only on right side in lower back
I can feel the contractions tho, its like stronger than a menstrual cramp
Theyre not coming regularly tho, just wasnt sure if they typically come on one side
If not reg then id say braxton hicks .. but yes they can be on just one side mine were