Advice on breastfeeding and or formula

Please help! This is my third and last baby, and she’s 4 1/2 mo old. My breastfeeding had been different for my first two children. Things seemed

To be going very well with my daughter up until about 3 1/2-4 weeks ago. She’s been waking up in the middle of the night every 2 hours (I kid you not). It’s worse than when she was first born. I am at a complete loss. I have heard about sleep regression but this has been going on and seems to be getting worse every day. She doesn’t really nap during the day because she’s woken up by my older two children. It just feels like I am not satisfying her with breast milk. I tried pumping the other day for 15 minutes and only got one ounce. I never was able to pump a whole bunch of milk. I am thinking about going out and getting some formula for tonight. Maybe try a bottle and see how things go following a breastfeeding session. I just do not want to be starving my baby. That’s basically what was happening with my first daughter. This all happened within the first six weeks of her life though and I switched to formula and she was great. It should be a clear answer right, but I am struggling and feel like I am failing. Any advice would be great. Thank you.