thank you both for the kind replies.
the problem with my partner is that he (ironically the one who wished to go into polyamory) is not the best communicator. his "meltdown" was due partially due to life stresses (job, money, etc) and partly due to having two people demanding him to communicate and express his affections, his commitment and put in the time. could this be a sign that he is not the right person to enter polyamory? is this just his own adjustment?
he never had problems being affectionate and caring and passionate, but he always has this 2 months a year in which he becomes detached. he calls it "becoming bored of being with the same person" - reason why he expressed the wish for us to become polyamorous. now i am wondering if the root of the problem isn't really the multiplicity of people, but his own issues.
he seems to be ok again, showing affection and even telling one of our friends (who then secretly told me) that he loves me and that he likes this person he is seeing but it isn't the same. it made me wonder if somehow some problem he might be having w her spilled over and that is why he collapsed last week.
if you have any further ideas on this, please let me know. I am getting in touch with some people in the poly community where i live (specially through okcupid) which is great because i get to exchange ideas, and obviously meet potential new partners.
the funny thing in the end is that, i was the one who thought i could not do polyamory and here i am, enjoying the experience, being out there, meeting people, etc. i still am not sure if i could have significant others besides my partner (that is, lovers who are more than just friends and sex) but that remains to be seen.