Every time you enter the UK as a visitor, you are admitted for a new period. For example, suppose go to the UK and receive a six month leave-to-enter stamp in your passport. Two months later, you go to France for the weekend. When you return to the UK, if they admit you, you will normally get a new six-month stamp in your passport.
However, you are not allowed to live in the UK as a visitor. If you're spending more than half of your time in the UK, you will eventually arouse the suspicion of a border officer, in which case you might be admitted for a shorter period or refused entry altogether.
I reentered at Dublin on may 6th and was given a 6 month visa for my stay in Britain.
Dublin, of course, is not in the UK, although they are both part of the "common travel area." Normally, if you enter through Ireland, you only get a three-month admission.
You should therefore double-check your Irish passport stamp and plan accordingly.
Spouse visas are generally off topic here; if you have plans to move to the UK to be with your boyfriend permanently, you should ask about those at Expatriates.
As an aside, your terminology is a bit off. The UK does not have a "visa waiver program"; this name is used by the US and (with different spelling) by Ireland, but not by the UK. Instead, the UK lists several countries whose nationals do not require visas to enter the UK; these travelers are referred to as "visa-free nationals."
Similarly, when you are stamped in at the border, you are not being "given a visa," as you write, but rather you are being given leave to enter. The visa is a sticker placed in your passport before you travel to the UK, so the ink stamp placed in your passport at the border is not a visa. (Some countries use different terminology, confusingly, but this distinction also holds for Schengen countries, the US, and Canada, at least.)