Cookie, interesting about sleeping around before settling down. IMO, there is not enough of this and, I think, this leads to affairs in the future.
I suppose the best analogy is a child in a sweet shop who wants to sample all the varieties before deciding which one to settle with. If you try enough you will realise they all are good to begin with, but too many and the initial buzz disappears ( I realise the analogy is falling apart here so will move on) - If you have a number of relationships, then you know they all start with the same heady buzz and 'feeling a million dollars', but then settle down to varying degrees of contentment.
If you have done this before marriage/settling down in a monogamous relationship, then I think you are less likely to stray as you realise the benefit is short term and not worth the disruption they cause the your life (also the odd crush can give you some of the same feelings without the downsides)
Sleeping around can be very self-empowering or self-destructive, depending on where you were mentally at the time and what it was trying to achieve.
Most teens/young people feel they have very little control in their lives and will try and find things which they can control - if this was you, then it can be empowering as control in this area enabled you to take the uncertainties in the rest of your life.
However promiscuity can be an attempt to get security from another person (ie love/affection) and this can drive accepting more and more abusive behaviour from others as you 'fight' to keep them happy and looking after you.
As Charbon said, you can only be responsible for yourself and therefore need to learn self-love and respect to take into a relationship - this is then (hopefully) reinforced by your partner.
This is easy for some, who have good familial and parental support than others that lack this, hence children in care are more vulnerable to abusive behaviour.
Only you can answer which explanation suits your circumstances (or whether they are both cant)
Regardless of this, you are where you are and can build yourself to a position where the loss of your partner (either through infidelity or death) would not destroy you. There are enough threads on here to make me be aware of 'what would happen if I were alone tomorrow?' and have a vague awareness of my options. This, I think, makes me more relaxed about worrying about my partner.
Think that's enough unrelated babble from me - as you were 