What is the downside of not having the correct dosage of penicillin? I have been prescribed 4 tabs a day for 2 weeks and there have been a few days I have forgotten and/or not taken all the full dosage. Does this mean that I am prone to an antibiotic allergy which I understand is a complete nightmare.
(Flucloxacillin 250 mg capsules)

I don't know what the possible problems of missing doses are.
But you need to take the full prescription.
Also take probiotics or eat organic unsweetened yogurt to replace the essential bacteria that the antibiotics deplete. Do not take them at the same time. Like if you take the antibiotics at 9 am and 6 pm take the probiotics between noon and 1. Or you can do the probiotics after the prescription runs out.

The downside of not taking your antibiotics as prescribed is that the illness for which you took it in the first place is not completely killed off and may be lying in a dormant stage. When it becomes active again it will be resistant to the penicillin. This is one example of why we now have such a large amount of MRSA in the general population.

Thanks guys - I guess I should continue to finish the dosage now even though because of the missed medication they will go on for more than the original 2 weeks - I guess that is less important(?)

Exactly