Is an itchy scalp and hairloss a side-effect to stress, and how long does it last?

If your hairloss is due to stress it would be due the stressors 4 months ago. Telogen effluvium or resting hair loss has a delay of about 3-6 months before the hair actually falls. It falls then because the hairs are regrowing in the hair follicle actually pushing out the old hair. So you would be growing hair not losing it even though all you see is the hair falling. The itch is likely unrelated. The tattoo removal is likely unrelated. It doesn't mean you are still stressed.