condom broke!

I engaged in receptive anal sex two nights ago with a bisexual guy who told me he is not HIV positive but I have no proof of that and don't know whether he has ever been tested.  I have always practiced safe sex but unfortunately this time the condom broke.  He said he heard the condom snap when he pulled out and that he did not ejaculate inside me.  I went to an urgent medical center the next morning (yesterday) and was put on combivir for 28 days.  That meant I took my first dose within about 14 hours of the event.  The urgent medical center told me to get an HIV test at 6 weeks with two followups at 3 months and 6 months. I had an HIV test two weeks ago and was negative. Can anyone please answer these questions for me?
1. Is PEP is appropriate here?  If so, is combivir alone enough or should I ask for another drug to combine with it? So far I haven't noticed any side effects and worry that adding another drug may result in bad side effects.
2. What do you think my odds of infection are?  I feel like I'm doomed.
3.  What does an HIV test as early as 6 weeks tell you?  Would most people who were infected show up positive at that time? Would a negative then be a good sign of no infection?
Thanks for responding to this.

[Teak]

1. Yes
    Combivir® (AZT and 3TC in one pill) or Combivir® plus Crixivan® doesn't   matter really. Combivir is good enough by itself.

2. I don't play the odds game. PEP is 85% effective.

3. Most that are positive will show up at 6 week. A negative at 6 weeks is not conclusive at 3 months it is conclusive. You are asked to do a 6-month test due to possibly being infected by a known HIV+ person. Those are the doctor's prerogative time line.

[anxious07]

Thanks for your quick response and taking the time to answer a frightened person like me.  You are obviously a good soul and I wish you the best.

[anxious07]

I saw my doctor again today and showed him the cdc guidelines which now recommend a three drug regimine for PEP.  These guidelines are posted at http://www.cdc.gov/mmwr/PDF/rr/rr5402.pdf  He apparently had never seen these guidelines and called the disease experts at our local hospital who recommended I add Sustiva to my combinir which I did today (which is day 4 of my PEP).  Although these guidelines say there is no evidence at this time that 3 is better than 2, they give some logical reasons to think 3 could be.  I have a couple of questions:  
1. Could you tell me what you think of their reasoning and why you instead think 2 is as good as 3?  
2. To my relief, I haven't felt any adverse symptoms so far on the Combinir but the Sustiva has made me very drowsy.   What have you heard about Sustiva's side effects?  Thanks for your help.