Have I been very stupid?

Okay guys. I was on 10 mg of Lexapro from January, increased to 20 mg in April, then stopped taking it for about a month after I got ill and accidentally left my medication at university.
Today I restarted at 20mg. About 2 hours later I suddenly felt very nauseous, vomited once, and had diarrhoea. However, I’d also accidentally drunk spoiled milk in an iced coffee about 1 - 2 hours beforehand (couldn’t taste it because of the coffee and syrup).
I felt much better after vomiting, but the nausea has come back.
Do you think this is more likely from restarting 20 mg after a month off, or from the spoiled milk? I’ve never had nausea from Lexapro before, so I’m not sure which is more likely.

I also only discovered today that 20mg is not really a low dose and that your not meant to start back on it at 20mg 😬