Ferrite core StepUP Transformer Design
You are way-off in your expectations. The peak flux density you will see is over 7 teslas and that's about 15 to 20 times more than what ferrite can handle: -

Peak voltage = 150 volts
Inductance = 4 turns squared x 3300 nH = 53 uH
V/L = 2.83 amps per micro second
At 100 kHz (and 50% duty) the peak current is 14.15 amps
Magneto motive force (MMF) = amps x turns = 56.6 At
H = MMF / core effective length (0.21 m) = 270 At/m
B = μr μ0 H = 2100 * 4 π * 10^(-6) * 270 = \$\boxed{\text{7.125 teslas}}\$

Too much flux density by a mile for ferrite (normally limited to 0.4 teslas) and I'm not surprised you are seeing a massive current because the core is strongly saturating.
I've just noticed that your switching frequency is actually 50 kHz and this means my number for peak flux density is low by a factor of 2:1 (even worse).

If my calculation is all wrong what you suggest I should be doing to
generate 100000 Volts at 28 milliamps?

If you are trying to get a 100 kV DC output then limit your transformer to producing an RMS output in the mid-kV range i.e. 3 to 5 kV AV and then use a Cockcroft-Walton voltage multiplier on the output that is oil-immersed and I don't mean cooking oil.
The reason I point out about limiting the transformer AC output is that with the number of turns needed, the insulation between secondary layer and the leakage inductance, you'll just about avoid hitting the self-resonant frequency of the transformer. If you hit SRF then you'll get really big problems that you'll never control.
$$\color{red}{\boxed{\text{Be aware - this sort of design can kill you in an instant}}}$$

I once designed a 50 kV power supply for an X-ray machine and plenty of days I got cold feet and stress during initial prototype testing. It could produce 4 mA but it was a scary beast. I had my load (and CW multiplier) immersed in a big oil bath and you could see the oil churning with the volts when I was operating at full wack. You should never do this on your own - you need someone in the room with you with a long stick that can press the on-off button on the DC power supply in case you start to fry.