Hi, as said in the title, DD is just 5 years old. She has been having tantrums for the last 3 years and they don't seem to stop. We are lucky if we find ourselves with a day without any tantrums 
We are not able to identify any triggers to this behaviour. Today, for example, it started in the bath. She has a little scratch on her back, DP was preparing the bath and she had started saying the she didn't want a bath because her back hurt. DP then said that she could have a shower and that we would keep her back dry. It follow the same that happens every time, "but I want a bath" " but I want a shower" (not able to make a decision or maybe she is just looking for the argument). At the end DP empty the bath once and had to fill the bath again as per her request.
Bath time, DD got in the bath and I was washing her body without wetting her back. She started shouting that she wanted a shower to which I replied that she was having a quick wash and she threw herself in the bath with her back in the water
. When I finished she started saying that she didn't wanted to come out so I lifted her out. She went back inside the bath saying that she wasn't coming out
. I lifted her out again and emptied the bath before she got back in.
This carried on for the whole bed time. She was screaming her head off, stamping and she even threw the water bottle down the stairs. She calmed down after 50 minutes approx and went to sleep. Not without complaining that she was thirsty to which I explained her that if she was thirsty she should have not thrown the bottle down the stairs. I gave her some water in the kitchen and she went back to her room to sleep.
We have started a new way of handling this situations in the last two weeks. If these tantrums occur during the day, we warn her that her behaviour is not appropriate. If she carries on, we tell her that we don't talk with her while she is behaving this way and ignore her which she very quickly composes herself and changes her behaviour. We praise good behaviour and give marbles as she likes this (her school uses this and she loves it). Unfortunately we have not been able to get to 20 marbles in her pot yet 
Bed time is more difficult to ignore as she needs to go to bed, so we don't do ignoring. We just get her ready for bed and leave her in her room. This means that sometimes we have to put her a few times in her room as she gets out. What we do at bed time is warn her that if her behaviour carries on she won't have a bed time story but in reality this doesn't stop her behaviour even though we follow the threat. We also warn her that we will take marbles from her pot but again this doesn't work even when she sees us removing marbles from her pot.
We are in desperate need of ideas please. Should we consider professional help? She is doing well in school. We had parents evening last night and for what they told us, they must have a completely different child to the one we leave in school and pick up 
Thanks in advance