Or is this even normal?
I would say 95% of the time I get on very well with my DP however every now and then, particularly if I'm very tired or have PMT I get very grumpy and sometimes get quite sensitive to anything my partner says which leads to some sort of small argument. We don't shout at each other or anything, it just gets a bit whingey. I would say I get a bit grumpy like this on average once a week or more.
Are most relationships like this or am I just very bad tempered?