Ouchhh
To me it looks like the agency you've hired is feeding you st - you can NOT get an appointment with the embassy, you have to submit your application PERSONALLY at VFS (see the the link posted by ScottishBride) as you have to undergo the biometrics - fingerprint scan and digital full face photography.
These times they do not do interviews very often - haven't heard of anybody interviewed on this forum recently, I guess they do them just when the circumstances are unclear and there is not enough support documentation and evidence provided by applicant (about relationship etc. etc.)
I would advise you to request all the paperwork (documents, letter of support, evidence of your relationship) back from the agency as it seems to me that they are really only after your money and do it on your own.
It is not so difficult to compile all the evidence and paperwork necessary - especially with the goldmine of information and advice found on this forum
I think if you will manage to apply sometime till the end September (earlier better & safer = you will get a bigger time margin) you should be alright and by December you could be in here in UK.
But - have to remind you - there were major delays at the visa section at the embassy recently (we ourselves been waiting for fiancee visa for 17 weeks ). I think it might be good idea to mention your pregnancy in the additional information or in the separate letter to the embassy included in your application - they might look at your app favourably and it might speed it up a little (but do not bet on this too much).
Wish you good luck