how am i supposed to know if its contractions?

FTM to be...38 weeks today and im having these tightening and sharp pains throughout my belly and pelvis. Ive never been pregnant before and I have never felt a contraction before but everyone keeps asking me if its contractions and I have no clue! 
How am i supposed to tell? Im so tired of everyone saying that I will just know....idk how im supposed to magically know when im having contractions if i dont know what they feel like and im also supposed to time them? How? This pain has been consistent today its not coming and going so theres nothing to time. 
Please help!!! Actual descriptions of contractions and not comments about just knowing would be helpful