Why do I always think my husband is cheating on me?

Well this depends. If he has given you a reason to not trust him then our first thought is always to assume someone will do something they have before again. Best to talk to your husband explain your insecurities and get a better understanding of eachother.

Sometimes there's this sense of anxiety in the air by my previous experiences I have been honest and asked them straight out because they do not have enough time to bluff or lie .

Anxiety and being paranoid can trigger this. If a husband is to work late shifts or be out with his friends late and he is later than a time he given to you can trigger paranoia and anxiety to rise. It can cause alarm bells and make you believe things that are not necessarily true. I'd sit down and talk and then you may get reassurance

It could be a number of reasons. Has he given you reason not to trust him the past? Do you feel like he loves you? Do you feel anxious about other things that you don't know the answer to? If you feel like you don't trust him or trust that he loves you, I would try talking to him about why and what you can do together to strengthen your trust and bond. If you think it's more anxiety than anything else, I would try explaining that to him and then perhaps working with a listener or therapist to mitigate it.

you could be experiencing paranoia, it could also be a lack of trust in the relationship which you can help with communication

You either have as a personal characteristic not being able to trust people due to past experiences or simply your personality or He shows lack of interest or attention in your relationship (It could still ba problem with him and not cheating)

It was proved psychologically that if you like you are being cheated on then it is a true feeling, but someone it’s not, if he is either too distant or too close then it might be a sign of cheating or he might become so protective over the phone in an unusual way.

I don't think he is I just think he conversates with females and flirts with them on his phone while at work or not around me

I understand people can be very protective, but you have to let people out of their shells. A husband should be open to their wife and tell them everything, not keeping everything open to your wife could result in bad things in the future. Tell him and discuss it at one point. And if he actually is cheating, he does not deserve you.

Why do you think that is how you feel? Has something happened before? Does he often text or see other women? Identify the surrounding factors and discuss them with your partner.