Just try not to worry about it. You're there to do your thing and what matters more, your health and strength, or the remote possibility that some guy who may or may not work in your department, might possibly be intrigued by what you're doing?
Let's face it there's plenty of other females there, so it's not like you're the only one, or it's probably not like the rest of the females do loads of cardio and you're the only one lifting weights, I would presume, otherwise you might feel a bit self conscious of a lot of cardio junkies possibly casting aspersions on your lifting, but I suspect others lift as well.
You're not being irrational, you're just being human, so it's perfectly okay to feel like you do, but just don't let it worry you that much. The only problem I think you might get was if a guy walked in and started transgressing any boundaries, I:E making disparaging comments about how you should be on a treadmill and lifting isn't for you, or saying slightly amorous things that they shouldn't say, in which case just ignore it, or politely tell them not to bother you, but I doubt that's happened I would suggest.
Be proud of you what you're doing and don't let anything about it get inside your head if you can

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I'm proud of you and have been since you first came here and told us what your life was like, so
WELL DONE and stick with it, because you've earned those feelings of pride and a sense of greater fulfillment and betterment of self.
