UPDATE!!!!im jealous about my husband's coworker!!!

The things is my husband had been botheing me for like 3 months straight that he was so tired of  his current job, that he hate it and was thinking about quitting etc... Basically its because the company has been bought for another bigger company and there have been a lot of changes,  they are short on people, same pay (salary) annoying new bosses etc. he was really commited to find a new job he was searching a lot.  
 And then like 2 weeks ago I noticed my husband wasnt complaining about his job at all! He even told me he was happy there.  So he hasnt been looking for one either... i didnt give it too much thought until I noticed my husband was saying too much the name of this girl which I know is at the front desk, they text each other more lately not always about job. She just got her brother a job in the company and my husband has being helping him a lot with anything! (And to be honest my husband is not the kind that helps others) 
And just recently she got offered the same position as my husband which pays better than what she does so of course she took it and they are both working on the night shift which annoys me! 
I feel so insecured lately so I told my husband what I noticed And he said that there's nothing to worry about but I can't help feeling this way, I have a gut feeling and I dont know what to do.... someone could give me an advice or tell me what you think!? 
UPDATE----------- My husband and her kept texting each other. The other night she texted him with an excuse of job at 11:30pm 😒 
  he was sleeping so I took his phone and answered saying he was sleeping and that I was his wife and she didnt answered back. 
So I had a HUGE  blow out and I confronted my husband about him possibly being emotional involve with this woman and he flipped out!! He got really defensive and got mad at me, and made me totally believe that Im right about it. 😭 I feel terrible!