I work as an automated test developper at a small company. I regularly get very good offers at jobs nearby and I have a policy to always take every interview I am offered simply because you never know what you might get. I never tell my boss, unless I am seriously considering switching jobs. I feel like garbage whenever I tell my boss that I can't really pass up a 15% raise with better benefits, but to my surprise, he always offers to raise me to what other companies offer me. I do very good work and have been implementing testing frameworks and techniques that never had been tried at the company and the results show, but I feel like trust is deteriorating (with reason). My question is (Pick one and elaborate): Should I leave the company to avoid this mistrust? Should I stay and stop taking interviews? Should I stay and keep doing interviews? So far it's been very effective and my salary skyrocketed for a 21 year old. This is my first question, so edit as you see fit.
This question sounds a lot like humblebragging as I'm sure you're somewhat aware, but there seems to be some meat here nonetheless.
Here's the thing: If your boss knows that you are interviewing elsewhere while working for him as well, then he knows your loyalty is split between him and whatever new shiny offer comes along. He knows (because you've told him) that you are getting better offers elsewhere and, more importantly, are actively thinking of taking them rather than staying at his company. Think of what you would do in his shoes: If you had an employee who is doing good work, but is also only half-working (and half-interviewing elsewhere), would that make you feel comfortable in that employee's likelihood of sticking around? Would that make you comfortable in possibly giving that employee a promotion if that employee might the next day come to work and hand in their resignation? Or how about if that employee is on a long-term project and halfway through just up and quits on you and now you're a man down on a large-scale critical endeavour?
It seems relatively clear why the trust is deteriorating (and I'm sure you're aware of this too). As for what you should do about it, you should, as they say, "put up or shut up". Make it clear to your boss what your intentions are. If your intentions are to stay with the company, then stop taking interviews and focus on the job you have. If you feel like you are underpaid, overworked, or something else, then bring that to the attention of your boss and let him know that you want a raise/increase in benefits/decrease in workload/whatever, and if he denies you your request, then you can start interviewing (although if you're going to start interviewing again you have to do so with full intention of actually leaving). That, or, just leave. If you feel like you could get paid better elsewhere or find a position you really like elsewhere, then go elsewhere.
Right now, your boss is on eggshells regarding your position, because he can't allocate you to anything important in case you decide to just quit at any point. So to relieve your boss of the stress, you need to decide if you're going to stay (and stop taking interviews) or leave, or else the lack of trust will only increase.
It seems that your current employer think you are doing a good job but won't change anything about your salary or tasks if YOU don't tell him you have better offer. They are putting away the fire instead of making sure there won't be ones.
What I would advise is to talk to your current boss before doing more interviews. Talk with him about your financial expectations, title, benefits, job tasks and all the things that other offers appealing to you.
Make you both aware of the things you hope for each other in the future. There is something that make you go to those interviews. Are you bored in your current job? Are those new ones offering paragliding every Friday? Do you want to buy a bike and would welcome more money?