Is this normal?

Nati • My description, your challenge
Ok so my husband & I are hoping to concieve in july and we are taking all the steps such as; eating healthy, geting fit, have a savings and starting next month I'll barely start taking prenatal pills. 
I'm very worried though because I've noticed that since January 2015 my periods have not been on time as usual, is this ok???
Why are they becoming so far apart?
I am starting to get very anxious & worried 😔
Jan 3, 2015    (43 days)
Feb 15, 2015  (36 days)
March 23,2015
If my period is so off, how to know when is a good time to concieve?