I'd say speak to a GP and look into counselling. Also, maybe explaining to your housemates that you suffer with anxiety will make you feel better? That way they'll be aware and will be better equipped to help you deal with things.
I identify with your lecture/seminar issues so, so much. I also sit near to the front and also on the end whenever I can. I have friends who sit with me and they just know that I don't like not being near the front or on an end. This time last year, I'd never have spoken in a tutorial group of about 10 people, let alone in a lecture in front of goodness knows how many people. I'm on medication now and have had counselling and even though I definitely still get a bit nervous about speaking in these situations, I choose to do it when I have something to contribute and slowly but surely, it's getting better.
Even if you don't have to do any presentations, I'd still recommend speaking to your lecturers/teachers one-on-one. I had one tutor last year who I told about my problems and he was so understanding and made a point of checking how things were going every now and then.