So sorry to hear about your neg beta
I was going to say that I had what I thought was a weird AF on the first cycle post my cancelled DE IVF. It came a the right time, was more like heavy spotting but I blamed the hormonal stuff I had to do in prep for the DE cycle. A week later I wanted to get rid of the lone HPT in my cupboard --just get it out of my life so it could stop staring at me every time I opened the cabinet door-- and holy cow didn't it turn up pos. It seriously floored me.
So naturally, when I started ttc my #2 (with mixed emotions of guilt and apprehension but that is another post)
a week after every AF no matter how heavy, I'd POAS. I bought them by the hand fulls from saveontests. OPKs too. I found deep satisfaction on POAS, I tell ya LOL
Took me 4yrs minus a month to finally get my + and then took us about 3yrs for our #2 miracle. And when I say 3yrs, its actually longer than that but I started counting once AF came back to me. my #2 it was closer to 3&1/2 but for my sanity I counted by AF cycles
HAng in there, IF sucks and it's full of ups and downs (I know, I'm preaching to the choir) and sure, let yourself mourn this cycle otherwise it'll eat you up. Mourning is a big part of IF.
What helped me was to do positive visualizations and to pep-talk myself and to count my blessings (I can't tell you how often I had myself convinced that sure, DH and I are happy, that having kids would enrich our lives no doubt but dang we are happy happy and to get on with it) and stuff like that. Some months it didn't work and I faked it (my moods) but some months it worked and kept me plugging away at this dream.
I am sharing this with you, not to discourage you, not to preach but, I guess to say only you know how to keep your head afloat. Do what you need to do.
sending you love and warm wishes that you'll have your dream come true really (freakin') soon