My girlfriend doesnot love me as much as i do for her after we have a lil kid. What can i do.?

When we both started i never had the intension we will come this far, she got pregnant for me at the stage and time we both not ready, i never denied and stood by her,when she gave birth the love i have for her grewup faster than ever, the boy is 2yrs old now and my plan is to settle down with her and the lil boy and a happy family. But nowadays she form some kind of irrational attitude that piss me off, its like she is tired of me and have been a nice guy, am confused dont know what to do.