What Causes Delayed Periods Along With Severe Mood Swings And Nausea?

hello my cycle usually starts on the 5th of every month for the passed 6th months, before that i was not getting a cycle do to my meth addiction but it's been extremely regular until now idk if my drug problem may play a part in it but i was 18 days late except its brownish lit red spotting an i've been having naseua sensitive smell extremly moody an this wierd flutter in my stomach which were all symptons i had when pregnant with my daughter the last time i had sex was from the 6th to the tenth of this month any comments