Extremely irregular :/

my husband and I have been trying for our second child for 2+ yrs :l it's really frustrating because I'm super irregular,so when i miss my period for like 2-3 months I don't know weather I'm pregnant or not so I take the test and negative..so far I haven't had a period in like 4or5 months:/ all tests have come back negative. Any suggestions? How can I get a little more regular? Should I be concerned about the length of time between my periods?