Cocker behaving oddly

Question
QUESTION: I have a  3yr old working cocker spaniel, though she doesn't intact 'work' as we have lived in town since she was 8months. She has been spayed.  Every so often, haven't noted how often, could be once a month or so, she starts panting and has a mad look in her eyes like she really is mad/neurotic and follows me around the house very closely, sits right by my side when I am sitting.
She doesn't get walked everyday, I walked her yesterday for just over an hour and we spent the rest of the day in the garden, that evening she seemed to have a sore leg but couldn't find anything she limped for a bit I put her foot in salted water and she was fine but then she yelped about half an hour later when she got up to move and hardly moved for the rest of the night. Today she is moving fine but ocasionally starts panting excessively and very clingy, which as I said has happened before. I have just taken the bins out and took her with me and usually she is very obedient, desperate to please but when she is in these moods, she is not.  
Would like to know your thoughts on this please and is this something you have heard of before?  Her mother was black and not weird like this, is it a brown trait?
Kind regards,
Jo

ANSWER: you don't say when this began so how long ago did the panting/clinging begin?

Unless this leg injury looks better within a day I think the vet needs to x-ray it.  Keep her quiet - no walks.

Where does she sleep?  How often is she fed?

---------- FOLLOW-UP ----------

QUESTION: Thinking about it probably since she has been spayed. She sleeps in the utility room in a cage, with the cage door open. She is fed once a day at about 4pm.  Last night when I thought she was in pain I did have her up on the sofa, usually she is not allowed up on the sofa and never upstairs.  So as I write this it could be hormones or when you give them an inch they take a yard?
Appreciate your thoughts.
Kind regards jo

Answer
And how long has it been since she was spayed?  It sounds to me like she's reacting "on schedule" as in having a heat.  That shouldn't be happening.

First (for a lot of reasons) I suggest you feed her twice a day

And, if possible, let her sleep near you.  The panting & clinging can mean anxiety and allowing her to sleep "with her pack" may help.

I hope the leg is looking better?