I did lots exercise (running, swimming, yoga, pilates, zumba, etc) when my baby was really quite young (the majority between 2 and 6 months) and I was ebf. I bought a sports bra in the correct size - that was the main essential. Breastfeeding immediately before exercise was helpful for comfort in the early days, and also reassured me that she would be fine while I was out for a run or whatever. When she was really little my boyfriend would come with me to the swimming pool, I'd feed and then go for my swim, while he had a little walk or cuddle with her. Then I wasn't leaving her for as long.
If you're playing football I assume it's in the evening? This is a bit trickier as lots of babies cluster feed in the evenings. However as time goes on you may notice more of a pattern - for example my baby almost always slept between 7ish and midnight at a few months old, so I could have gone out then. (I am no good at exercising in the evening though!)
The leaking won't go on forever.
It's still really early days - by summer you'll be starting weaning and as she takes to food other people can offer a yogurt or something instead of a breastfeed.
I don't know how long you're planning to bf for, or whether you're just going to wait and see, but in my experience bf at 9 months is absolutely incomparable to breastfeeding at 8 weeks. I still bf my baby at 18 months, and it doesn't alter my life in any way at all. I wear my normal bras, do whatever sport I want, eat and drink whatever I want, go away for the night if I want, work night shifts, etc.
It's such early days! Congrats on your lovely baby and think about sport when you feel up for it - I certainly found breastfeeding no barrier at all.
ps. I found expressing a huge waste of time and am not going to bother for 2nd baby. As they get older babies can be surprisingly adaptable as to timing of feeds.