I have been making the same recipes with fresh ingredients(leavening agents, flour etc) for years and suddenly NOTHING, not bars, cookies or any cakes are baking properly in my oven. The oven is less than 5 years old and a wall unit Frigidaire.  I made two cakes, 9x13, for a friend’s birthday and while they both rose beautifully and fully during cooking,  when I took them out they were half the pan!  I made a batch of blondies and they too did not rise and the center was raw.  I let the bars cook longer to complete the center however the edges were inedible.  When I eyeball items midway through and they look done I then check the center and they are finished in half the time!  Do I need a new oven?  Help I am starting to feel like the worst baker on the planet!!
thanks!

Welcome.  Gee, it sure seems likely that your problem is your oven.  Get yourself an oven thermometer so you can manually adjust the temp.

In the meantime, why don’t you call the manufacturer and also the place where you purchased the oven to see if they they will offer you an extended warranty - then have the repairs done.  That’s what we did when my husband broke the interior door glass on my KitchenAid oven - the oven was 3 years old and the warranty cost less than the price of the replacement glass not including the labor.  Oh, another idea is to call your local utility company to see if they offer a service/repair plan of some sort for major appliances - there’s a gas company in MN that covers the service on many major appliances for just a few dollars a month.

It’s very interesting that sometimes your oven seems slow/too cool and others seems very fast/hot.  Assuming that your oven doesn’t have hot/cold spots, it seems like the thermostat could be broken. 
Good luck with repairs!

I had a similar problem with my oven last Christmas. Sometimes it would heat well and other times not so well. Fortunately I have an oven thermometer in my oven permanently and was able to monitor the temp. Turned out that the igniter had to be replaced. Mine is a JennAir gas oven. The technician told me not to use the self-clean cycle too often, which I am guilty of doing.

Patricia, how did your husband manage to break the glass on your oven???