I'm confused,could I be pregnant?

I had sex on the 30th march which I didn't realise until I checked after was my ideal conception date. I've been feeling a little strange since then. About two days after this I started getting really bad pains in my lower abdomen,so bad I couldn't move, so I went to the doctors and he did a urine dip stick test which he said showed possible signs of infection but nothing dramatic, so he put me on antibiotics anyway and said to some back if it got worse,in the meantime he sent off for a full urine test.the results of which still haven't come back yet. On top of this,my period was a week late, my breasts are reeaally sore, it feels as though milks coming in!this is unusual for me because I don't get sore breasts normally. Certain foods like fish are making me feel ill just at the thought of them. Also this period is unusually painful,I've got lower back pain and pain all accross my abdomen,spreading down into my thighs.the period I'm having also isn't quite as heavy as usual, but wen I realised my period was late I did a test and it came up negative, but im not convinced!could I be pregnant?