Injured...

Ever since I started running I've had several niggly injuries, but nothing too bad.
Anyway, for a couple of weeks my left calf muscle has been tight when I've got up on a morning, and when I've been running on the treadmill at the gym for the first 10-15mins of each run that and my left shin have ached (they haven't when I've done an outside run strangely). I've been doing stretching exercises and it seemed to improve a little, but after yesterday's workout it was actually hurting. I think it could be my achilles but not sure with me getting an ache in my shin as well.
I iced it when I got home and tried to sort of massage it and it has improved a lot overnight, but is still definitely not right.
I should have been going to my step class at lunchtime and I was going to go as I'm still trying to make up for my bad weekend away, but when it came down to it I knew that if I did I'd just make it worse. My first 5k race is in 10days and I really need to be able to do it. This is just so hard because I don't know what to do for the best. On the one hand I need to just keep pushing myself on the exercise front and hope I can work through it, but on the other I know that if I keep pushing I might have to stop exercising altogether for a while if this injury gets worse, and if I can't do the race then months of hard work will have been wasted.
I'm sat here icing it again at the moment and hoping that it's better still tomorrow and I can still go and do my last chance workout at the gym. But the pessimist in me is worried sick I'm going to miss another workout... This is really causing me to panic and feel anxious. I've exercised consistently for at least 4 days a week during the whole of my weight loss journey and the thought of not being able to exercise at all fills me with terror that as a result the weight loss might stop or even go backwards...