Flyback converter losses
Note that primary winding does affect input losses. Your transformer design seemed a bit odd to me (61 turns primary for a 40kHz offline converter seems quite low).

So I re-designed your transformer:


Parameters: Vin: 85-265Vac = 120-370VDC, Vout=5V, Iout=5A, eff: %85 so Pin=25/0.85=30W, f = 40kHz (from your UC2844 config: RT=4k and CT=10n), maximum duty: %45 at minimum Vin, Total transformer loss=%5Po=1.25W and total core loss = 1.25W/2=625mW, core:EE28 (Ae=85mm², Ve=43cm³).


From transformer equation, \$V_t=N\cdot A_e \cdot dB/dt\$. 

For our needs, this equation turns to \$V_{inDC_{min}} = N_{p_{min}} \cdot A_e \cdot \Delta B/\Delta t_{max}\$ where \$\Delta t_{max}= 0.45 / 40kHz = 11\mu s\$. Assuming you're using 3F3 core, from 3F3 datasheet (Fig. 6), selected \$B_{pk}=80mT\$ for a core loss per volume of 625mW/43cm³=14mW/cm³. So \$\Delta B=2 \cdot B_{pk} = 160mT\$. 

With these parameters,
$$
N_{p_{min}}=\frac {120V\cdot 11\mu s}{85mm^2 \cdot 0.16T}=97
$$
So, if volts per turn is \$120/97=1.24\$ then number of secondary turns is \$N_s=5 \cdot 97 / 120 = 4\$. Supplying UC2844 with 15V is quite enough, so required number of turns for aux winding is \$N_a=15 \cdot 97 / 120 = 12\$.

For a current density of \$J=420A/cm^2=4.2A/mm^2\$, your wire selections are quite enough.

Besides, a few extras I can suggest: 


Place a 1k resistor across opto's LED for proper biasing. 
Although your feedback network is correct, I personally recommend you to connect FB pin and opto's emitter to GND, opto's collector to CMP. So you can get rid of R19, R20, R21 and C11.
D9 (Zener) is unnecessary since your auxiliary supply is regulated enough. 
Instead of C10-R18 snubber network, place a, 200V zener or so.


If you're interested, take a look at one of my offline flyback designs (32V/3A) and ST's application note.