If i have constipation, does this mean that i have irritable bowel syndrome?

Yes: You can have ibs-c which is with constipation, ibs-d with diarrhea or IBS with alternating constipation with diarrhea - total 3 types.

No: Constipation is common and diet related. Ibs is not common.

Depends: Either way, Metamucil or similar supplement is helpful, also be sure to drink more water, and get daily aerobic exercise at least 15 min daily.

Maybe: Constipation is often related to low thyroid function (despite normal labs) or a food intolerance that causes inflammation of the GI tract. Could also be magnesium deficiency. You can start with adding magnesium supplement, 250-500mg twice daily. In my practice, i find that constipation isn't usually due to typical 'dehydration and lack of fiber intake'. It's more likely due to above mentioned.