I am experiencing some severe under extrusion
Assuming your filament dimension settings are correct and your extruder is correctly calibrated...

Your extruder temperature may be too low.  While 184C can be hot enough, it is very near the bottom of the range for PLA and it appears your filament isn't melting quickly enough to keep up with your other settings.  Your extruder may even be running slightly cooler than you think so your 184C setting may actually be printing at 180C or less.

To solve this:


Raise your extruder temperature. I suggest raising your print temperature to 220 degrees and then gradually lower it until other aspects of your print quality are acceptable (bridging, oozing, etc).
Slow down your print. Slowing down reduces the volume of melted plastic your extruder has to deliver in a given amount of time.  This allows more time for the plastic to melt and allows you to use a lower print temperature


Your filament feed mechanism may be slipping.  Even if you have adequate temperature and perfectly calibrated firmware and print settings, if your filament feed mechanism (the thing that pushes filament into your extruder) is slipping, you will have under-extruded parts.

To solve this:


Make sure you have adequate tension on your filament feed mechanism.  If your feed mechanism is too loose, filament may slip and cause under extrusion.  The part to check is the part the pushes the filament into the rotating hobbed bolt or friction wheel...make sure it applies adequate pressure.  "Adequate pressure" or "adequate tension" will vary depending you your printer's design, but it should be enough to provide a firm grip on the filament.
Verify your feed mechanism is clean.  A hobbed bolt or similar filament drive mechanism that has become clogged or otherwise contaminated may cause filament to slip and under-extrude.
Ensure the end of your filament is not damaged from slipping.  Once your filament has slipped, it may be damaged with a worn spot, a bulge, or some other defect that can prevent proper feeding even after you fix the root cause of your problem.  So, as tbm0115 pointed out, be sure to clip off the damaged end to make sure you have good filament feeding into your extruder.


I hope this helps!