Will Irregular Periods Cause Problems In Conceiving?

hi im am 29 yrs old and i started having my periods when i was 13. Ever since i have never had them on a set date always 5-6 weeks or sometimes after 3 weeks - does this reduce my pregnancy chnaces? also is it possible to have periods at a set date? i am 5ft 3 inc tall and weigh 7 stones