Has anyone else experienced this?

Just wondering if this has happened with anyone else, I was on depo injection for 2 years and was due to have another in March 2015 but me and hubby decided to start trying for a baby! 
Anyway I didn't have my first period until January 2016, had another in Feb and according to this app I was due again Wednesday 23rd so now 4 days late ( went 35 days between Jan and Feb) did a test yesterday but was negative :-(