Hay fever and antihistamines

After several months of feeling down and generally depressed about life it turns out my antihistamine can impact mood in some people; and I have been taking it every day for months, something I've not done before.

I did have more than a few things in life that were depressing and caused me to over analyse, which I know I do, but for some reason I couldn't 'sort myself out' and get through it which I usually manage to do.

"Paradoxical Effects: In some individuals, particularly at higher doses, it worsens anxiety, restlessness, or agitation instead of calming. Long-term Risks: Regular use is linked to cognitive decline and memory risks, according to the NHS guidelines on anticholinergic drugs."