unexpected baby

Feeling depressed not expecting for baby #4 ive been nursing my 1yr old since now and February is the 1st menstruation i have ever since i gave birth i was expecting march 1st week for monthly menstruation though we used withdrawal method only and then march came and no menstruation came I took pt 20s of date in march turned negative and about last week of march feelings of pregnant goes by i took pt april 2 turns positive and i cant how come baby number 4 is coming where doomed financially and me physically although its a blessing .?