Sckoon or Lunette

Hello! I've never used a cup before and I was hoping for a little advice on what cup to get.the two I'm trying to decide between are the Sckoon cup or the Lunette. I'm 25 and have never had children but ever since I got the copper iud put in my cycle is extremely heavy and I get very strong cramps. Because of the heaviness of my cycle I'm inclined to get a larger cup even though I haven't given vaginal birth but because of the severity of my cramps I'm worried a firm cup will increase my cramps. Does anyone here use a large cup if you're under 30/childless and does anyone feel thir cramps increased by the cups? Also if you've used either of these cups id love to hear your opinion on which to get