Hi Julia,
I too had the same worries, my baby was concieved the day after my birthday and as you can imagine I had several drinking sessions before I found out I was pregnant. I was convinced I harmed my baby, but was told I shouldn't worry by my Dr and midwife. I am now nearly 21 weeks pregnant and my baby is doing great (is a right active bean). If you are not drinking now and have stopped/or reduced smoking then you are doing the right things.
I am so pleased for you on your BFP. I don't think what you did was irresponsible, in fact I think that may have helped you concieve as I know many people who have TTC'd for a while, decided to have a break and then get pregnant because they were relaxed. I am lucky and have not had to go through the horrible experience of a miscarriage but know someone who has and from what she has said I understand that previous miscarriages do not mean that you have a higher chance of miscarrying this time. I send you big hugs and a lot of love, and please don't worry about what you have done, just enjoy your BFP. xxxxxxxxx