Help & advice whatsapp mistery

Hi everyone,
I need help to think, because i cannot find a clear solution for myself in this question. Putting things simple i have reasons to assume my wife can be cheatting with a specific person. I dont have definitive proof, but some very suspicious things happen some months ago. I talked, she denies firmly. I know the person i suspect so i remembered to go to whatsapp and see last seen on whatsapp, and it always online in specific hours that: match her work time breaks, minutes before work start and when it ends, its creapy. Sometimes his number is "offline" hours, and then in 5 min break, or 10 min break he is online matching a work pause of her! Not once, almost everyday! Other coincidences happen in other situations (besides work). Her whatsapp isnt used in same timeline, but her work is different everyday and it is always matching.... in weeks. I thought she could be using other phone at work, but strange coincidences also happens when we go on holidays, or at weekends (example, sometimes when she goes to bathroom he stay online for the exact amount of time she is in there). So, it might not be other phone just on work, and i think it would be hard to have other phone at home, or in holidays without me to notice. Its not her phone because sometimes this happen with her phone off. I am not an abusive peson. I dont want to stay in this relationship if this is happening, but i cant ignore this issue also. Does anyone have an idea what might be happening? (one last example, this number stay online for the first time in the day almost everyday at our different waking up hours (in the different days of the week), and it is last seen almost at the same time at our sleeping time. If this is coincidence... probabilities and statistic here... its hard to understand. Any ideas? Any other device can be use to link with whatsapp besides tablet/phone/pc? Is SHE using his number using other device (in bathroom example she left her phone at the table)? Any thoughts?