1. Kyriaki says she confesses every few months, I've heard some say two or three times a year. Do you still receive communion even if you've not confessed for some weeks? I get the impression that you can't receive with unconfessed sin?
The only times confession is necessary before communion is if one has committed an egregious sin (adultery [including pornography], murder, apostasy, etc.), failed to go to communion for three weeks straight (which canonically excommunicates you until you confess), or if it has been a long time since your last confession (e.g. 4+ months).
It is NOT required otherwise, though obviously we sin enough that it isn't harmful. It would be harmful if someone thought it legally obligatory, but that would create an odd circumstance. IF we must confess before EVERY communion then, functionally, communion ex-communicates us (as the very act of communion requires us to go to confession before we take communion again).
The practice of frequent confession is good, but not ancient. It seems to have developed first in the monasteries (confession of thoughts to an elder) and then become imitated in the parishes centuries later.
I'll repeat: frequent confession is a spiritual boon; but not a legal requirement (like Rus said).
2. Particularly for converts that didn't have confession in their previous tradition do you find that, knowing you have to confess before your priest, that you sin less?
That helps for a time, but honestly the liberty provided by confession (e.g. the grace of the sacrament itself) helps even more. I still sin, though, which just turns into a double shame, as now I am without excuse.
To the OP: my first confession was a life-confession with the abbot of a monastery; we sat in an otherwise empty chapel and talked for over an hour. I had a prepared list, which I was then instructed to burn after my baptism (that is, after the absolution provided by baptism). It was harrowing, but one of the most liberating experiences of my life.
Confession face-to-face is high-risk and high-reward. It feels a bit like going to die (or at least, I like to think that my anxiety is the old-man in me anxious over his death). Seeing the compassion in my priest's face, though, and feeling his hand on my head making the sign of the cross during absolution - these are the physical representations of God's love and forgiveness. I can't imagine confession without them.
In Christ,
Macarius