Lindill49 I am so sorry you are suffering from this. It is a horrible thing to go through. I gather he has confused you concerning what/where he has been on a fairly regular basis and that if you dare touch the subject, even innocuously, as you did when you said you'd find something to do this weekend, he obfuscates and explodes in anger at you thus instantly closing down communication.
If this has been an enduring trait or repeated behaviour you only have two choices. Either you live with it or you tell him you are not going to tolerate being lied to and put down by angry outbursts anymore. At its least it is disrespectful. I think when trust has gone in a relationship the very basis of the relationship is threatened and the bond falls apart. What he is doing is abuse, lying and using threatening anger to shut you up as soon as you touch on the subject of his secret life. This is controlling behaviour.
I am wondering if he does any other things to control you. You may be unaware of what it means. We get so used to it that it seems normal - it happened to me. www.psychologytoday.com/gb/blog/friendship-20/201506/20-signs-your-partner-is-controlling
gives a list of examples but do look at other websites because you need to get a wider feel of it. Also, don't let him try to accuse you of controlling him, just because you asked about his plans. You have grounds to ask and it is a natural question. His reaction is very controlling and his refusal, repeatedly, to give you a satisfactory reply undermines trust.
Please seek counselling. Please. Do not try to live with this on your own. You say it is a small thing, but I think that is your way of trying to cope. I have the feeling it is niggling away at you a lot more than you can cope with and if you don't do something to resolve it, it could make you ill. You have reached out to us here. Please find a Counsellor, if you can a relationships counsellor. Your GP should be able to help.
There is one last thing that has been on my mind. There was a case of a man who was a cross-dresser and could not tell his wife. He had to get away regularly to join other men to relax in women's clothes and enjoy this side of his personality. I am not joking. If he has a need like this he must trust you and you must understand him and appreciate it is harmless. Ask him if this is so and tell him you love him anyway. Sending you lots of love ?