What Causes Delay In Periods, Giddiness, Backache And Breast Pain?

Hello Doctor,
My wife, 25 years old (married to me 2 years back) has missed her period by 5 days. Past four days she had all signs of pregnancy like giddiness, backache, pain near the breasts & stomach pulling. Today, i.e 5th day, while urinating, she observed little brownish bleeding at 4 a.m. she had not got bleeding till now (i.e till 8 p.m).
Please note we had not induldged in active sexual life till the 20th day of her period.
my queries:
1) What are the chances of her being pregnant?
2) Can me & my wife indulge in sexual life at this stage?
3) we have booked a movie ticket tonight, is it advisable to travel by bike to the theatre which is 3 kms way from home?
4) She's a housewife and what kind of tasks could be done?

Thanks & Regards
Expectant Father