Glow App Accuracy


I previously used the "<a href="">Period Tracker</a>" app because it's super user friendly and frankly, that's all I really knew at the time, a friend told me about it. Another friend referred me to the "Glow" app and I logged all my data from the <a href="">Period Tracker</a> app to the <a href="">Glow app</a>. At first the data was pretty spot on with a day off on ovulation dates. Glow said my OV date was 6/24 and <a href="">Period Tracker</a> 6/23 but the future period dates were the same, off by one day. Glow said 7/8 and <a href="">Period Tracker</a> 7/7. Well, as I went to track my chart today, I fat fingered the screen and accidentally marked today as my start date. (I haven't started my period yet so I tried to delete it) Well, the <a href="">Glow app</a> doesn't allow me to return to the previous data, it either marks 7/8 as my start of period date or delete the data for this day all together. So, now the app says my future Period is 7/9 and it changed my future OV date too. Why? Why would it change so drastically? All the dates are back to what I originally entered but now it's telling me I have 2 more days left before my period starts instead of 2 days late. Obviously, I prefer be 2 days late than 2 days away from my future Period. Why the sudden change? Has anyone else experienced this? How can I fix the issue? Is it an app malfunction or was my Glow predictions wrong the first time around.

All my home pregnancy tests come back negative but I haven't started my period. I have some symptoms but I'm not confident they are pregnancy symptoms. Womp, womp... HELP!

***Please take the time to respond if you have advice you can share***