GP treating me for depression 15 + yrs without any tests?

I was on paroxetine (seroxat) for 15 years. I asked my GP for a review as I was fed up suffering from poor concentration, extreme tiredness. My GP has now changed my medication to Citralopram (another anti-depressant of the same time). While I was weaning myself off Seroxat I did have some very good days. I told my GP this but she just said 'well, everyone gets good days' and told me to start the Citralopram. I commenced these about 5 days ago (half a tablet, with the intention of building up if I am okay with them). However, the last couple of days I have been feeling suicidal. I do not know whether to stop taking the Citralopram alltogether or to take a whole tablet (in case the half a tablet does is not sufficient). Please can someone advise. I am not feeling too bad at the moment but was very low earlier today. I asked to be referred to a psychologist but my GP just referred me to a local NHS self referral group (Gateway) who apparently have access to psychologists. However, they were not use as they just wanted me to go on a stress / anxiety course (which I couldn't go on as it was in the evenings & I do not go out in the evenings & am too sleepy to take anything in then anyway). In fact, they caused me to be even more stressed as they say you must pay attention on the course etc & if you do not comply and go on the full 6 week evening course then they will refer you back to your GP.